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A NiO/β-Ga2O3 heterojunction was fabricated by sputtering a highly p-doped NiO layer onto β-Ga2O3. This heterojunction showed a low leakage current and a high turn-on voltage (Von) compared to a Ni/β-Ga2O3 Schottky barrier diode. The extracted Von from the NiO/β-Ga2O3 heterojunction's forward current–voltage characteristics was ∼1.64 V, which was lower than the extracted built-in potential voltage (Vbi) obtained from the capacitance–voltage curve. To explain this difference, deep level transient spectroscopy and Laplace-deep level transient spectroscopy were employed to study majority and minority traps in β-Ga2O3 films. A minority trap was detected near the surface of β-Ga2O3 under a reverse bias of −1 V but was not observed at −4 V, indicating its dependence on hole injection density. Using Silvaco TCAD, the hole diffusion length from P+-NiO to β-Ga2O3 was determined to be 0.15 μm in equilibrium, which is increased with increasing forward voltage. This finding explained why the trap level was not detected at a large reverse bias. Moreover, hole diffusion from NiO into β-Ga2O3 significantly affected the β-Ga2O3 surface band bending and impacted transport mechanisms. It was noted that the energy difference between the conduction band minimum (CBM) of β-Ga2O3 and the valence band maximum (VBM) of NiO was reduced to 1.60 eV, which closely matched the extracted Von value. This supported the dominance of direct band-to-band tunneling of electrons from the CBM of β-Ga2O3 to the VBM of NiO under forward bias voltage. [ABSTRACT FROM AUTHOR]

The relativistic self-trapping of a laser pulse is an efficient mechanism for the acceleration of electrons, which allows one to achieve an extreme charge of a high-energy particle beam and the corresponding conversion coefficient of laser energy. It has been shown that the compression of the femtosecond laser pulse in this regime using the innovative compression after compressor approach (CafCA) [E.A. Khazanov, S.Yu. Mironov, and G. Mourou, Phys. Usp. 62, 1096 (2019)] to extremely short durations keeping the energy of the laser beam significantly increases the efficiency of particle acceleration. This effect has been illustrated on the example of the Multitera laser facility for the project implemented at the Russian National Center for Physics and Mathematics. [ABSTRACT FROM AUTHOR]

This study focuses on InGaZnO-based synaptic devices fabricated using reactive radiofrequency sputtering deposition with highly uniform and reliable multilevel memory states. Electron trapping and trap generation behaviors were examined based on current compliance adjustments and constant voltage stressing on the ITO/InGaZnO/ITO memristor. Using O2 + N2 plasma treatment resulted in stable and consistent cycle-to-cycle memory switching with an average memory window of ~95.3. Multilevel resistance states ranging from 0.68 to 140.7 kΩ were achieved by controlling the VRESET within the range of −1.4 to −1.8 V. The modulation of synaptic weight for short-term plasticity was simulated by applying voltage pulses with increasing amplitudes after the formation of a weak conductive filament. To emulate several synaptic behaviors in InGaZnO-based memristors, variations in the pulse interval were used for paired-pulse facilitation and pulse frequency-dependent spike rate-dependent plasticity. Long-term potentiation and depression are also observed after strong conductive filaments form at higher current compliance in the switching layer. Hence, the ITO/InGaZnO/ITO memristor holds promise for high-performance synaptic device applications. [ABSTRACT FROM AUTHOR]

Double perovskite La2FeCrO6 (LFCO) powders were synthesized via the hydrothermal method, which crystallized in an orthorhombic (Pnma) structure and exhibited a spherical morphology with an average particle size of 900 nm. Fourier transform infrared spectroscopy demonstrated the presence of fingerprints of vibrational modes of [FeO6] and [CrO6] octahedra in the powders. The XPS spectra revealed dual oxide states of Fe (Fe2+/Fe3+) and Cr (Cr3+/Cr4+) elements, and the oxygen element appeared as lattice oxygen and defect oxygen, respectively. The LFCO powders exhibited weak ferromagnetic behavior at 5 K with a Curie temperature of 200 K. Their saturation magnetization and coercive field were measured as 0.31 μB/f.u. and 8.0 kOe, respectively. The Griffiths phase was observed between 200 K and 223 K. A butterfly-like magnetoresistance (MR)–magnetic field (H) curve was observed in the LFCO ceramics at 5 K with an MR (5 K, 6 T) value of −4.07%. The temperature dependence of resistivity of the LFCO ceramics demonstrated their semiconducting nature. Electrical transport data were fitted by different conduction models. The dielectric behaviors of the LFCO ceramics exhibited a strong frequency dispersion, and a dielectric abnormality was observed around 260 K. That was ascribed to the jumping of electrons trapped at shallow levels created by oxygen vacancies. The dielectric loss showed relaxation behavior between 160 K and 260 K, which was attributed to the singly ionized oxygen vacancies. [ABSTRACT FROM AUTHOR]

Chromium-doped persistent luminescence nanoparticles (PLNPs) have promising biomedical applications in X-ray charged near-infrared (NIR) luminous imaging. The persistent luminescence (PersL) property was usually adjusted by co-doping with other ions. Impurity phases were thought to be adverse to the PersL. In this study, a composite material, LiInSi 2 O 6 :Cr,Pr·2SiO 2 (LICP-S), was synthesized with a PersL peak at 800 nm after being charged by 1 Gy X-ray while LiInSi 2 O 6 :Cr (LIC) and LiInSi 2 O 6 :Cr,Pr (LICP) possessed no or very weak PersL. Distinctively, excess metastable cristobalite silica was found essential for the much more intense PersL of LICP-S than LICP and LIC. Thermostimulated luminescence spectra studies indicated that cristobalite adjusted the Pr-related traps from deep traps to shallow ones, which facilitated the room temperature PersL. The low dose X-ray charged PersL of LICP-S was applied to demonstrate the luminous labeling of a medical silicone prosthesis that was supposed to be imbedded in body for years via X-ray activated PersL imaging in vitro and in vivo. This work not only provides a kind of PLNPs with 800 nm emission suitable for low dose X-ray activation, but also an unusual strategy for trap engineering in PersL materials by designing multi-phase composites. Metastable cristobalite SiO 2 induces 10-times enhanced NIR persistent luminescence of LiInSi 2 O 6 :Cr,Pr after X-ray activation. [Display omitted] [ABSTRACT FROM AUTHOR]

Conventional spectroscopies are not sufficiently selective to comprehensively understand the behaviour of trapped carriers in perovskite solar cells, particularly under their working conditions. Here we use infrared optical activation spectroscopy (i.e., pump-push-photocurrent), to observe the properties and real-time dynamics of trapped carriers within operando perovskite solar cells. We compare behaviour differences of trapped holes in pristine and surface-passivated FA0.99Cs0.01PbI3 devices using a combination of quasi-steady-state and nanosecond time-resolved pump-push-photocurrent, as well as kinetic and drift-diffusion models. We find a two-step trap-filling process: the rapid filling (~10 ns) of low-density traps in the bulk of perovskite, followed by the slower filling (~100 ns) of high-density traps at the perovskite/hole transport material interface. Surface passivation by n-octylammonium iodide dramatically reduces the number of trap states (~50 times), improving the device performance substantially. Moreover, the activation energy (~280 meV) of the dominant hole traps remains similar with and without surface passivation. Conventional spectroscopic techniques are not sufficiently selective to follow the dynamics of trapped carriers in working perovskite solar cells. Here, authors use infrared optical activation spectroscopy to observe real time evolution of trapped carriers and compare the behaviour of trapped holes. [ABSTRACT FROM AUTHOR]

The perovskite polycrystalline thin film detector fabricated by solution method is a promising low‐cost, scalable technology for radiation imaging, but its thin volume limits the sensing efficiency for high‐energy X‐ray photons. This work reports 2D perovskite thin film photo‐diodes with a detection gain when sensing visible and X‐ray photons. Detailed power and temperature‐dependent device characterizations reveal a charge multiplication effect to be responsible for the observed high gain. This is caused by a disparity in electron and hole transport, where electron transport is retarded by a trap/de‐trap process via shallow trap states, whereas the hole transport is fast enough to produce a photoconductive gain in satisfying the charge neutrality. The 2D perovskite made with butylamine spacers is also found to exhibit a larger efficiency gain than those made with phenylethylamines because of the higher likelihood of forming shallow traps in the former. The thin film diodes feature a high temporal response over 1 MHz due to the fast charge collection across a thin volume, and the discovery provides device physics mechanisms in connection to material structure‐function relationship for future optoelectronics design that can boost the efficiency of X‐ray sensing and dim light detection. [ABSTRACT FROM AUTHOR]

In a two‐step procedure for fabricating perovskite films, the PbI2 layer formed on the substrate is converted to perovskite by reacting PbI2 with organic iodide. Excess PbI2 left after forming perovskite composition, however, might have an ill effect on device stability and current–voltage hysteresis, although it positively affects efficiency improvement. Additive engineering is reported here on to control the residual PbI2 in a two‐step procedure. A series of organic multi‐ammonium chloride derivatives are introduced into the PbI2 precursor solution for the first‐step coating, which results in an increase in the perovskite grain size. In addition, carrier lifetime is elongated due to the reduced trap density and the energetics are adjusted to facilitate the extraction of photogenerated carriers. The aminoguanidinium‐containing precursor leads to an improved power conversion efficiency (PCE) as compared to the bare PbI2 precursor mainly due to the significantly enhanced open‐circuit voltage and fill factor. Consequently, a PCE of 23.46% is achieved from the hysteresis‐less photovoltaic parameters and 93% of the initial PCE is maintained after aging for 1000 h in ambient conditions. [ABSTRACT FROM AUTHOR]

In this paper, the RF and analog performances of the triple material gate (TMG) step Fin (SF) FinFET, step drain (SD) FinFET, and step source (SS) FinFET have been explored by 3D TCAD simulation. We have simulated the performance in the presence of uniform trap (UT) and Gaussian trap (GT) distribution with a fixed value of trap concentration (1012 eV−2cm−2). The various DC parameters, such as threshold voltage (Vth), sub-threshold swing (SS), and switching ratio, are observed in trap distribution. The outcome of this simulation study is that the SF FinFET structure has shown 25.1% and 33.95% enhancement of drive current compared to SD FinFET and SS FinFET, respectively. On the other hand, SS FinFET has shown an enhancement of 1.2x(9.8x) on gain transconductance frequency product (GTFP), 1.21x(1.01x) of transconductance frequency product (TFP), 4.19x(23.28x) of intrinsic gain (Av), 1.88x(21.21x) of gain frequency product (GFP), and 4.18x(9.69x) of the gain-bandwidth product (GBP) compared to SD FinFET (SF FinFET). [ABSTRACT FROM AUTHOR]

Reversible and repeatable control of rare earth ions doped down-shift luminescence materials induced by the external field stimulation can be applied more widely. However, there is still a challenge on reversible luminescence regulation of photochromism-induced rare earth ions doped down-shift luminescence materials by light fields stimulation. The MoO 3 : Eu3+ phosphors changed color from light green to blue due to the formation of color centers caused by the trapping of electrons by oxygen vacancy defects under near infrared irradiation at 808 nm, and recovered from blue to initial light green after heating at 500 °C, showing a reversible change in color. The down-shift luminescence intensity of MoO 3 : Eu3+ phosphors reaches the maximum quenching degree, about 87%, after 20 s irradiation by 808 nm laser, which has the characteristics of fast response and great regulation rate. Moreover, the down-shift luminescence intensity can recover to the initial intensity after heating at 500 °C for 90 s, indicating reversible regulation of photochromism-induced down-shift luminescence. The application of MoO 3 : Eu3+ phosphors as the anti-counterfeiting labels and information storage of binary encoding was designed, these results suggest that it have certain potential applications in anti-counterfeiting and optical storage field. [Display omitted] [ABSTRACT FROM AUTHOR]

This work analyzes the effects of a nearby Hf or Zr dopant on the electron density trapped at an oxygen vacancy site. The two metals are among the dopants used to achieve thermoluminescence and energy storage in phosphors based on cubic lutetium oxide (c‐Lu2O3). The presence of oxygen vacancies is anticipated in those phosphors. If the dopant is located outside the immediate surroundings of the vacancy site, the resulting optical trap depth is similar to that of the isolated oxygen vacancies (1.6–1.7 eV versus 1.7 eV). If the dopant is one of the four metal cations surrounding the vacancy site, the corresponding trap depth is 2.0–2.1 eV. Using time‐dependent density‐functional theory calculations, it was found that the excitation of the vacancy‐trapped electrons can take two forms: a local excited state at the vacancy site can be formed, or an electron transfer to Hf might occur. With charge compensation in mind, several structures with three defects were analyzed: the dopant cation, the vacancy and an interstitial oxygen (Hf/Zr plus a Frenkel pair). These last two systems with the dopant in a +4 oxidation state and a single electron trapped at the vacancy site correspond to zero total charge, while another electron can be trapped. The vacancy site is expected to trap the electron, not the dopant. The composite defects of the dopant and Frenkel pair are thus considered the most likely electron traps in cubic Lu2O3:Hf and cubic Lu2O3:Zr. [ABSTRACT FROM AUTHOR]

We present a design and a fabrication method for devices designed for rapid collection of nanoparticles in a fluid. The design uses nanofluidic channels as a passive size-based barrier trap to isolate particles near a central point in the channel, which is also covered by a thin membrane. Particles that enter the collection region are trapped with 100% efficiency within a 6–12 μ m radius from a central point. Flow rates for particle-free fluid range from 1.88 to 3.69 nl/s for the pressure and geometries tested. Particle trapping tests show that high trapped particle counts significantly impact flow rates. For suspensions as dilute as 30–300 aM (20–200 particles/ μ l), 8–80 particles are captured within 500 s. [ABSTRACT FROM AUTHOR]

In this research, we investigate the integrability properties of the Schamel–Korteweg–de Vries (S-KdV) equation, which is important for understanding the effect of electron trapping in the nonlinear interaction of ion-acoustic waves. Using the optimal system, we come over reduced ordinary differential equations (ODEs). To deal with reduced ODEs for this problem, Lie symmetry analysis is combined with the modified auxiliary equation (MAE) procedure and the generalized Jacobi elliptic function expansion (JEF) method. The analytical solutions reported here are novel and have a wide range of applications in mathematical physics. [ABSTRACT FROM AUTHOR]

Photonic synaptic transistors are being investigated for their potential applications in neuromorphic computing and artificial vision systems. Recently, a method for establishing a synaptic effect by preventing the recombination of electron–hole pairs by forming an energy barrier with a double-layer consisting of a channel and a light absorption layer has shown effective results. We report a triple-layer device created by coating a novel electron-trapping layer between the light-absorption layer and the gate-insulating layer. Compared to the conventional double-layer photonic synaptic structure, our triple-layer device significantly reduces the recombination rate, resulting in improved performance in terms of the output photocurrent and memory characteristics. Furthermore, our photonic synaptic transistor possesses excellent synaptic properties, such as paired-pulse facilitation (PPF), short-term potentiation (STP), and long-term potentiation (LTP), and demonstrates a good response to a low operating voltage of − 0.1 mV. The low power consumption experiment shows a very low energy consumption of 0.01375 fJ per spike. These findings suggest a way to improve the performance of future neuromorphic devices and artificial vision systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen-modified g-C 3 N 4 with nitrogen-defect was successfully synthesized. • N -defect as electron trap inhibited recombination of photoinduced electron and hole. • Introduction of oxygen-containing functional group improved the hydrophily of g-C 3 N 4. • Absorption bands derived from n → π* and π → π* electronic transitions were enhanced. • Evolution rate of H 2 O 2 catalyzed by g-C 3 N 4 -ND4-OM3 reached 146.96 μmol/g/L. Photocatalytic oxygen reduction is regarded as the cleanest approach for the production of hydrogen peroxide (H 2 O 2). Herein, oxygen-modified graphite carbon nitride (g-C 3 N 4) with nitrogen-defect (namely g-C 3 N 4 -ND4-OM3) was synthesized by a feasible method. Owing to the existence of nitrogen vacancy and oxygen-containing functional group, the absorption bands derived from n → π* and π → π* electronic transitions were enhanced, thereby enlarging the visible light response range of catalysts. Interestingly, nitrogen-defect can capture electron and effectively suppress the recombination of photoinduced electrons and holes. More importantly, the introduction of oxygen-containing functional groups can improve the hydrophilicity of g-C 3 N 4 , which was beneficial for the adsorption of dissolved oxygen. The electrostatic potential distributions of g-C 3 N 4 -based photocatalyst structural unit were also changed after introducing nitrogen vacancy and oxygen-containing functional group, and the electron-donating ability of g-C 3 N 4 was improved. As a result, the evolution rate of H 2 O 2 catalyzed by g-C 3 N 4 -ND4-OM3 was as high as 146.96 μmol/g/L under visible light irradiation. The photocatalytic H 2 O 2 generation was completed through the direct 2-e− oxygen reduction. In short, current work will share novel insights into photocatalytic H 2 O 2 generation over g-C 3 N 4 -based catalyst. [ABSTRACT FROM AUTHOR]

Although doping organic fluorophores into host matrix is a common way to obtain high‐efficiency organic light‐emitting diodes (OLEDs), trapped charges are often observed on dopant molecules that are considered to be detrimental to the further enhancement of their photoelectric performances. Surprisingly, trapped charges with a super‐long lifetime of >2 h are detected in doped OLEDs operated at 20 K, which has never been discovered previously in the literature. However, the observations demonstrate that the longer lifetimes of these trapped charges are primarily governed by the larger spacing distances between trapped electrons and holes, rather than being solely determined by the well‐accepted energy‐level depth of trap states. More amazingly, compared with the device driven only by a conventional constant voltage source, a tenfold enhancement in light emission is achieved in low‐temperature operational doped OLEDs powered by an alternating positive and negative pulse voltage, because the applied negative pulse voltage can assist these super‐long‐lived trapped electrons and holes to detrap and then recombine with each other for producing enhanced light‐emission. Therefore, this study clarifies the dynamic behaviors of trapped charges and paves the pathway for obtaining high‐performance OLEDs working in low‐temperature circumstances such as outer‐space or aerospace fields. [ABSTRACT FROM AUTHOR]

A novel ultra‐sensitive gold‐coated tungsten‐coil atom trap coupled with HGAAS was developed for the first time for the determination of arsenic. The analytical methodology was based on transporting and in‐situ trapping of arsine produced by the hydride generation system onto a gold‐coated W‐coil trap for preconcentration via Ar and H2 gases. The trap surface was examined using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. SEM images revealed that the surface is covered with hexagonal and pentagonal structures on a micro scale with gold. The experimental parameters were optimized for both trap and non‐trap method. The enhancement factor for the characteristic concentration (C0) was determined to be 15.3 when compared with the non‐trap methods. For the trapping time of 120 s using the developed method, the limit of detection (LOD) and the precision were determined as 4.8 ng L−1 and 3.6 %, respectively. The interference effects of various hydride‐forming ions were examined in detail. The accuracy of this ultrasensitive methodology was successfully verified by analysis of certified reference materials and some drinking water samples.. t‐test was implemented to the water samples, the added and measured concentrations exhibited no statistically meaningful distinction at the 95 % confidence level. [ABSTRACT FROM AUTHOR]

The sustainable conversion of mechanical energy into light (elastico-mechanoluminescence, EML) opens up possibilities for energy-saving, which is of pivotal significance in addressing the energy crisis. The concepts of piezophotonics and the piezoelectric field's dependence on the probability of charge carriers detrapping have been thoroughly developed in explaining EML. Nevertheless, in contrast to the EML triggered by the piezoelectricity model, strong elastico-mechanoluminescence phenomena have also been frequently discovered in non-piezoelectric materials. Is the working principle different? This paper provides physical insight into the reconfigurable EML phenomena of intrinsic non-piezoelectric systems. It emphasizes the exploration of the mechanism through comprehensive analysis of trap information, de-trapping processes, and the lifetime of charge carriers in traps. We demonstrate the assistance of deep trap to enhance the red EML mode in a diphase centrosymmetric luminescent host through the electron tunneling effect. This advancement supports the progress of non-piezoelectric EML dielectrics and offers an appealing alternative approach in this field. [ABSTRACT FROM AUTHOR]

Confinement time of electron plasmas trapped using a purely toroidal magnetic field has been found to exceed 100 s in a small aspect ratio ( R o / a ∼ 1.59 , R o and a are device major and minor radius, respectively), partial torus. It improves upon the previously reported confinement time by nearly two orders of magnitude. Lifetime is estimated from the frequency scaling of the linear diocotron mode launched from sections of the wall, that are also used for mode diagnostics. Confinement improves as neutral pressures are reduced to < 5 × 10 - 10 mbar in the presence of a steady state magnetic field of 200 Gauss ( ∼ 60 s with droop < 0.1 % ) at 100 V electron injection energies. With reduced pressures the role of (ion driven) instability diminishes and loss mechanisms resulting from elastic electron–neutral (e–n) and the ubiquitous electron–electron (e–e) scattering seem to play an important role which suggests low electron temperatures. The contribution to electron population resulting from the ionization of background neutral gas at these temperatures and pressures are expected to be insignificant and is corroborated in our experiments. [ABSTRACT FROM AUTHOR]

Persistent luminescence (PersL) phosphors are considered as promising candidates for the next generation of information storage medium. Mg4Ga4Ge3O16 (MGG) is an electron trapping material which exhibits defect luminescence, and the luminescent properties are easily tuned via doping various activated ions. In this work, undoped and Mn2+/Pr3+/Tb3+ single‐doped MGG phosphors were synthesized via high temperature solid phase reactions. X‐ray diffraction and scanning electron microscope results confirm that the activated ions tend to occupy Mg2+ sites. Excited at 265 nm, the MGG host exhibits a defect emission band peaked at 450 nm. Red, pink and green emissions are observed in the Mn2+/Pr3+/Tb3+ single‐doped MGG samples, which are ascribed to the Mn2+: 4T1(G) → 6A1(S), Pr3+: 1D2 → 3H4 and Tb3+: 5D4 → 7F5 transitions, respectively. All the samples exhibit bright PersL for minutes after the cessation of excitation. The energy transfer, concentration quenching, luminescence decay and afterglow mechanisms are also discussed in detail. The phosphors exhibit efficient thermal and optical stimuli response, showing great potentials in the optical information storage. [ABSTRACT FROM AUTHOR]

X‐ray luminescence spectra, thermally stimulated luminescence, and thermally stimulated conductivity of undoped cesium iodide (CsI) crystal are investigated in order to reach better understanding of the factors which govern the emission processes in this material. X‐ray luminescence spectra are recorded in the temperature range from 15 to 293 K. The low energy band at 2.2 eV emerging at heating above 120 K is assigned to the emission of residual impurities. Other two bands peaking at 3.6 and 4.3 eV at 15 K are attributed to the intrinsic emission of CsI due to the self‐trapped excitons (STEs). The parameters of the peaks observed in the thermally stimulated luminescence and conductivity of CsI crystal are calculated. Investigations of the thermally stimulated processes in CsI lead to the conclusion that the increase of luminescence of 4.3 eV observed above 70 K is due to release of trapped electrons, which subsequently interact with Vk centers and form on‐center STEs. The considerable ionic conductivity observed above 250 K can be explained by the influence of uncontrolled impurities of divalent metal atoms as well as Na+ ions. [ABSTRACT FROM AUTHOR]

Single particles trapped in an optical trap may experience temperature elevation, yet direct measurement of temperature and its distribution inside the optical trap of several to hundreds of microns in size remains a big challenge. We introduce a method that can measure the temperature inside a universal optical trap (UOT) using Raman spectroscopy of single trapped particles of high thermal conductivity. We measured temperature and temperature distributions inside the UOT using Raman shifts of single-walled carbon nanotubes (SWCNTs) and micron-sized diamonds (MSDs), which are heated by trapping laser beams directly or indirectly, depending on the location of the particle in the trap. We show that the temperature at the center of the UOT is much lower than the temperature along the hollow beams that form a hollow, cage-shaped UOT. In the range of the trapping laser power of 200–2950 mW, the surface temperature of particles trapped at the center of a UOT changes from 322 K to 830 K, correspondingly. This result gives a heating rate as a high thermal-absorbing particle trapped in the center of the UOT with 18.3 ± 0.4 °C/100 mW. In addition, the temperature gradient outside the UOT was also characterized by trapping SWCNT particles outside the UOT. Results show that when a light-absorbing particle is trapped for the study of material property, phase transitions, surface equilibrium process, chemical reactions, etc., this method can be used to measure temperature distribution and its variations in the trap and its surroundings. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

High‐energy physics community is looking for a hard, fast, and low‐cost scintillation material, and Ce:Lu3Al5O12 (Ce:LuAG) ceramic is one of the competitive candidates. This work presents Ce,Ca:LuAG scintillation ceramics with good optical quality, and the influence of Ce and Ca concentrations on optical and scintillation properties was fully analyzed. At relatively low level of Ce concentration, the less Ca2+ content is needed to achieve a significant intensity increase in fast scintillation component while maintaining a relatively high light yield (LY). The introduction of only 0.1 at% Ca2+ could increase the LY0.5 μs/LY3.0 μs from 79.9% to 96.1% in Ce,Ca:LuAG ceramics of 0.1 at% Ce. First‐principles investigations are further performed to reveal the tuning mechanisms of the scintillation properties of LuAG by Ce and Ca codoping. We show that the Fermi level shifts down with Ca codoping, which increases the Ce4+ content and decreases the depth of the electron traps (VO), resulting to a faster decay. Moreover, the formation preference of Ca‐VO complexes over Ce‐VO leads to the suppression of the non‐radiative decay of Ce via VO. In summary, our study demonstrates the realization of the performance tuning of LuAG via Ce and Ca codoping. [ABSTRACT FROM AUTHOR]

The electronic, optical, and magnetic properties of Nd-doped ZnO systems were calculated using the DFT/GGA + U method. According to the results, the Nd dopant causes lattice parameter expansion, negative formation energy, and bandgap narrowing, resulting in the formation of an N-type degenerate semiconductor. Overlapping of the generated impurity and Fermi levels results in a significant trap effect that prevents electron-hole recombination. The absorption spectrum demonstrates a redshift in the visible region, and the intensity increased, leading to enhanced photocatalytic performance. The Nd-doped ZnO system displays ferromagnetic, with FM coupling due to strong spd-f hybridization through magnetic exchange interaction between the Nd-4f state and O-2p, Zn-4s, and Zn-3p states. These findings imply that Nd-doped ZnO may be a promising material for DMS spintronic devices. [ABSTRACT FROM AUTHOR]

We consider nonstationary diffusion in a medium with random traps-sinks. We study the self-averaging of the mean-square displacement (MSD) of the ensemble of N particles in the fluctuational long-time limit. We demonstrate that MSD of survivors is self-averaging with respect to the number of engaged particles N and is strongly non-self-averaging with respect to time t. To measure MSD of survivors with required accuracy at the required time of observation t 0 , the initial number of particles N 0 must be exponentially large in t 0 . Any N 0 , whatever large, will be insufficient at long enough time. In the formulation, when all particles, both survivors and trapped ones, contribute to MSD, we find self-averaging in N and non-strong non-self-averaging over t. [ABSTRACT FROM AUTHOR]

The fabrication of a cadmium sulfide (CdS) thin film has been carried out by the chemical bath deposition method under two different conditions, namely, without UV light (nonexposed) and with UV light (exposed). The thin films were found to be uniform, smooth, and homogenous under both growth conditions. Structural and microstructural studies were carried out to understand the mechanism of thin-film growth. Under both conditions, the CdS thin film was found to be face-centered cubic structured. The UV light-exposed CdS thin film acquired acicular or flower-like over structures embedded in the continuous thin film of CdS. The optical band gap increased for the UV light-exposed CdS thin film. In addition, the dark and light currents also increased around 6 times for the UV light-exposed thin film compared to the nonexposed UV light thin films. The highest photosensitivity for the nonexposed and exposed UV light CdS thin film device was ~ 200% and 230%, respectively. A decrease in the photocurrent was detected and probed as a result of traps and the recombination of electrons and holes. Our findings suggest that photoexcitation during chemical reactions could be used as an effective tool to modulate the growth process and, in turn, to tune the optoelectrical properties. [ABSTRACT FROM AUTHOR]

Interfacial electron transfer plays an important role in the boosting photoactivity of heterojunction under sunlight irradiation. Here, the lattice oxygen migration etching Ag-doped perovskite induced self-assembly ternary heterojunction 0D/2D/1D Ag@Ni(OH) 2 /La(OH) 3 via hydrothermal treatment. The LaNiO 3 controlled self-assembled into Ni(OH) 2 /La(OH) 3 heterojunctions at the interface and constructed a semi-coherent interface. Furthermore, it became reinforced quaternary heterojunction 0D/2D/1D/2D Ag@Ni(OH) 2 /La(OH) 3 /g-C 3 N 4 by electrostatic self-assembly with g-C 3 N 4. The novel constructed Z-scheme heterojunction Ag@Ni(OH) 2 /La(OH) 3 /g-C 3 N 4 promotes the effective separation of photogenerated carriers. The semi-coherent interface between Ni(OH) 2 /La(OH) 3 promotes the transfer of photogenerated carriers. At the same time, the silver nanoparticles on Ni(OH) 2 nanosheets act as electron trapping sites to further improve the photocatalytic performance. In this way, the synthesized photoexcited quaternary heterojunction Ag@Ni(OH) 2 /La(OH) 3 /g-C 3 N 4 showed an outstanding hydrogen production rate from photocatalytic water splitting (the yield of hydrogen was 1633 μmol/g/h) under simulated sunlight. It is comparable to many g–C 3 N 4 –based photocatalysts known at present. • The Ag@Ni(OH) 2 /La(OH) 3 from La 1-x Ag x NiO 3 is synthesized by top-down and bottom-up methods. • The semi-coherent interface of Ni(OH) 2 /La(OH) 3 is constructed for carrier transport. • The Z-scheme and Ag nanoparticles promote charge separation. • The 0D/2D/1D/2D Ag@Ni(OH) 2 /La(OH) 2 /g-C 3 N 4 boosts the photocatalytic H 2 evolution. [ABSTRACT FROM AUTHOR]

Conjugated polymers offer flexible and lightweight solar cells devices which are fabricated via cost-effective solution processing techniques; however, these devices suffer from lower efficiency and short-term lifespan. To improve the efficiency and stability of device, the knowledge of the mechanism of the sun light absorption, dissociation of excitons into the free electron-hole pair and their transport to the collecting electrodes are essential. Herein, the impact of PCBM concentrations on photophysical and optical and properties of PTB7 were investigated by spectroscopic ellipsometer and fluorescence spectroscopy. It was noticed that with increase of PCBM concentrations, the dielectric constant (εr) and refractive index (n) of PTB7 thin films decreases which ascribed to the reduction of electric polarization and increase of the surface roughness. The emission intensity was noted to be dropped and charge carrier lifetime decreases for PTB7:PCBM bulkhetrojucntion as compared to pristine PTB7, confirms the charge transfer between donor and acceptor. The charge transport mechanism in PTB7 thin film was investigated in hole only device architecture by recording the temperature-dependent current-density vs. voltage (J–V) curves. The charge transport for the temperatures above 220 K was governed by the trap-free space charge limited (SCL) conduction described by Mott-Gurney square law and switched to the trap-filling SCL conduction for T ≤ 220 K. For the temperature 220 K, the trap density Hb, hole mobility µ and characteristics trap depth Et were evaluated to be 2.98 × 1017 cm−3, µ = 6.08 × 10−5 cm2 V−1 s−1and 25 meV, respectively. [ABSTRACT FROM AUTHOR]

Tenebrescence has been reported to have a high potential for personal ultraviolet (UV) detection. Color changes can detect UV doses and can also be used as visual sensors for X-rays. Hackmanite is known to exhibit tenebrescence. This study investigated the kinetics of electron-trapping levels contributing to the luminescence of Na8Al6Si6O24(Cl,S)2 hackmanite using thermoluminescence. The glow curves were measured at a heating rate of 5 K/s on hackmanite irradiated with X-rays. The physical parameters of the electron-trapping levels were evaluated by analyzing them using the deconvolution, peak shape, and initial rise methods. The Na8Al6Si6O24(Cl,S)2 hackmanite had at least five trapping levels, with activation energies of 0.78, 1.12, 1.86, 1.26, and 1.18 eV and corresponding peak trap lifetimes of 3.59, 2.71, 1.47, 3.34, and 3.91 s, respectively. The estimated migration time was 15.0 s. [ABSTRACT FROM AUTHOR]

X‐ray time‐lapse imaging allows for precise radiographic imaging of the item after X‐ray has been terminated, which is important for simplifying legacy X‐ray detectors and avoiding health hazards caused by ionizing radiation during the imaging process. However, the premature discharge of carriers from shallow traps at room temperature over time leads to the loss of imaging information, making an accurate representation of the recorded information to achieve accurate time‐lapse imaging still a challenge. Here, it is demonstrated that monodispersed NaLuF4: Tb3+ nanocrystals with the replacement of Na+ by Cs+ ions in the lattice matrix realize a superior X‐ray time‐lapse imaging. It is found that the incorporation of Cs+ ions amplifies the deep trap storage capacity, which ensures the stable presence of carriers under thermal perturbation at room temperature. Imaging information with a spatial resolution of 12.0 lp mm−1 can be accurately represented even after the irradiation of the X‐ray has been terminated for 192 h. X‐ray time‐lapse imaging not only allows accurate reading of long‐term stored imaging information but also endows the visualization of X‐ray imaging independent of the dangerous radiation, which will offer great opportunities for X‐ray inspection on a larger scale. [ABSTRACT FROM AUTHOR]

In this paper, a series of K5La1-x(MoO4)4: xSm3+ and K5La0.86(MoO4)4: 0.07Sm3+, 0.07Ln3+ (Ln = Sc, Y or Gd) red phosphors were prepared by calcining the mixed raw powders at 600 °C. Meanwhile, the composition and fluorescence properties of the phosphors, especially for the thermal stability, were analyzed in detail. The results indicate that the K5La1-x(MoO4)4: xSm3+ phosphors can be effectively excited at 401 nm and emit red light with three main peaks at 561 nm, 600 nm and 646 nm, attributed to the 4G5/2→6Hj/2 (j = 5, 7 and 9) energy transitions of the Sm3+ ion respectively, among which the K5La0.93(MoO4)4: 0.07Sm3+ exhibits the highest intensity. The quenching mechanism is ascribed to the dipole-dipole interaction. Ln3+ co-doping does not change the shape and peaking position of the excitation and emission spectra of K5La0.93(MoO4)4: 0.07Sm3+, but further increases the emission intensity in different degrees. Particularly, K5La0.86(MoO4)4: 0.07Sm3+, 0.07Gd3+ demonstrates a high quantum efficiency of 74.63%, a low color temperature (1753 K), and a high color purity of up to 99.97%. It is worth noting that all the phosphors have a good thermal stability, even a zero quenching phenomenon occurs, attributed to the electron traps confirmed by the TL spectrum. [ABSTRACT FROM AUTHOR]

This study aimed to propose a silicon-on-insulator (SOI)-based charge-trapping synaptic transistor with engineered tunnel barriers using high-k dielectrics for artificial synapse electronics capable of operating at high temperatures. The transistor employed sequential electron trapping and de-trapping in the charge storage medium, facilitating gradual modulation of the silicon channel conductance. The engineered tunnel barrier structure (SiO2/Si3N4/SiO2), coupled with the high-k charge-trapping layer of HfO2 and high-k blocking layer of Al2O3, enabled reliable long-term potentiation/depression behaviors within a short gate stimulus time (100 μs), even under elevated temperatures (75 and 125 °C). Conductance variability was determined by the number of gate stimuli reflected in the maximum excitatory postsynaptic current (EPSC) and the residual EPSC ratio. Moreover, we analyzed the Arrhenius relationship between the EPSC as a function of the gate pulse number (N = 1–100) and the measured temperatures (25, 75, and 125 °C), allowing us to deduce the charge trap activation energy. A learning simulation was performed to assess the pattern recognition capabilities of the neuromorphic computing system using the modified National Institute of Standards and Technology datasheets. This study demonstrates high-reliability silicon channel conductance modulation and proposes in-memory computing capabilities for artificial neural networks using SOI-based charge-trapping synaptic transistors. [ABSTRACT FROM AUTHOR]

A study of the wakefield excitation in a magnetized quantum plasma is presented. The high-density plasma has been magnetized through a magnetic field applied in the longitudinal direction. Using a recently developed quantum hydrodynamic model and a perturbative technique, taking into account the quantum effects of Fermi pressure and Bohm potential, electric and magnetic wakefields were obtained for the Gaussian profile of the electromagnetic pulse. Electrons are trapped in the wakefields and accelerated to extremely high energies. It is observed that the quantum effects significantly affect the wakefield excitation. Quantum dispersive effects tend to reduce the acceleration gradient, whereas the external magnetic field helps with self-focusing and also contributes to acceleration. The axial and radial forces acting on a test electron have been calculated. [ABSTRACT FROM AUTHOR]

GaN‐based materials are the hottest research topic in UV photodetectors (PDs) because of their low operating voltage, small volume, long lifetime, high‐temperature resistance, and low energy consumption. However, there are still fundamental issues to be overcome, and the most important issue is to get a photoconductive gain. In this paper, the following new approaches are provided to innovatively improve the photoconductive gain of UV PDs in GaN‐based materials. First, the aspect ratio of the 1D GaN microwire (MW) structure is dramatically improved by analyzing the pulse growth mechanism using the metal‐organic vapor deposition system. Second, the comprehensive strain behavior in the MW epitaxial growth system is successfully analyzed. Third, the fabricated metal‐semiconductor‐metal‐based MW UV PD shows photoresponsivity and sensitivity of 28.365 A W−1 and 93.16%, respectively, at the −2 V bias, which significantly outperforms the conventional structures in the UV region. Finally, a trap‐assisted Poole–Frenkel effect‐based energy bandgap mechanism, that allows the defect level formed by lattice mismatch between the substrate and GaN to be used as an electron carrier path, is newly defined. This study will present the direction of future UV PDs by providing a new MW structure based on GaN materials, a third‐generation semiconductor. [ABSTRACT FROM AUTHOR]

Optical information encryption based on luminescence materials have received much attention recently. However, the single luminescence mode of the luminescence materials greatly limits its anti-counterfeiting application with high safety level. Here, a series of luminescence materials of Tb3+ and Bi3+ co-doped ZnGa 2 O 4 phosphors with great correspondence in photoluminescence (PL), persistent luminescence (PersL), and thermoluminescence (TL) modes was synthesized by the conventional solid-phase method for the application in multi-modal anti-counterfeiting fields. Under the excitation of 254 nm, ZnGa 1.99 O 4 :0.01 Tb3+, yBi3+ (y = 0.001,0.002) sample exhibited a broad blue emission band (the transition from [GaO 6 ]) at 440 nm and the characteristic emission peaks of Tb3+ at 495 nm, 550 nm, 591 nm and 625 nm, corresponding to the transitions of 5D 4 -7F n (n = 6, 5, 4, 3), respectively. Interestingly, the co-doping of Bi3+ ions improve the crystallinity and particle size of the phosphor, subsequently enhanced the PL intensity of Tb3+ to 6 times that of Tb3+ singly doped ZnGa 2 O 4 phosphor. Further, the flexible films with multi-modal luminescence properties have been fabricated through the unique TL and PersL characteristics of ZnGa 2 O 4 : Tb3+, Bi3+ phosphors, including "Optical information storage film", "snowflake and characters" and "QR code". Moreover, a set of optical information encryption is obtained by combining ZnGa 2 O 4 :Tb3+, Bi3+ phosphor and red emitting phosphor. The results indicate that ZnGa 2 O 4 :Tb3+, Bi3+ phosphor with multi-modal stimulus response can be expected to be potentially used in the applications of optical information storage and anti-counterfeiting fields. [ABSTRACT FROM AUTHOR]

Multimodal luminescence has emerged as a promising solution in the realm of anti-counterfeiting techniques, which have gained global attention due to their association with information and data security. The conventional approach to achieving multimodal luminescence typically involves combining upconversion and downshifting luminescence, which necessitates the use of external excitation sources and costly detection equipment. Herein, we develop an anti-counterfeiting strategy based on the afterglow performance of NaLuF 4 : Gd, Tm nanoparticles after X-ray excitation. The X-ray-induced Frenkel defects-base traps ensnare electrons with low kinetic energy, resulting in the creation of persistent photon traps that are responsible for the temperature-dependent afterglow intensity. The dual-band and thermo-enhanced afterglow emission can encrypt information well according to our proof-of-concept experiment and the visible light signal can be successfully captured by a smartphone camera. These unique features of NaLuF 4 : Gd, Tm nanoparticles render them highly appealing for multilevel anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

A study on comparison of two different light traps in an organic farming system was conducted in J-block of GKVK campus maintained by Research Institute on Organic Farming (RIOF), University of Agricultural Sciences, Bengaluru, Karnataka for understanding the proportion of pest and non-pest species of insects caught in a Solar light trap and an electric White LED light trap, by evaluating the various ecological functional groups of trapped insects. The experiment was conducted in the organic farm, University of Agricultural Sciences, GKVK, Bengaluru, India. The study was conducted over a period of 7 months from February 2022 to August 2022 in 14 days interval. The two traps were placed at a distance of 700 meters and run simultaneously for 12 hours from 6:45 PM to 6:45 AM. The trapped insects were categorized based on their feeding habits and taxonomic affiliations viz., herbivores, predators, parasitoids, scavengers, mycophages, pollinators and medically and veterinary important insects. A total of 4713 insects were trapped in Solar light trap among which, predators recorded 64 per cent, scavengers 27 per cent and herbivores 8 per cent. The White LED light trap caught 2795 insects in total, which included, predators 42 per cent, herbivores 28 per cent, scavengers 28 per cent and pollinators 1.14 per cent. In Solar light trap as well as White LED trap, greater proportion of non-herbivores (92% and 72% respectively) were trapped compared to herbivores (8% and 28% respectively). These results thus suggest potential harm to the local beneficial fauna and a consequent damage to the balanced agro-ecology. In this context, deployment of any type of light trap for the sole purpose of pest management is not a tenable option. [ABSTRACT FROM AUTHOR]

Herein, visible light‐driven gas‐phase photocatalytic CO2 reduction into CH4 is tuned by designing optimized three‐component Au/doped C3N4/TiO2 composite photocatalysts. The key point strategy consists in the formation of high‐quality C3N4/TiO2 heterojunction by associating low containing doped graphitic carbon nitride to commercially available TiO2 UV‐100. Those heterojunctions result in both visible light sensitization and increased charge‐carrier separation. Further deposition of small Au nanoparticles (≈3 nm), quite exclusively onto TiO2 surfaces, mainly acts as electron trapping/cocatalytic functions without excluding surface plasmonic effects. The resulting doped g‐C3N4 material exhibits enhanced visible light harvesting properties, especially in the case of C‐doping. In addition, it is assumed that B– and C–C3N4 doping, leading to a more or less lower conduction band position, is the impacting factor toward total CH4 selectivity achievement. The (0.77 wt%)Au/(0.59 wt%)C–C3N4/TiO2 composite photocatalyst, exhibiting the best compromise between the various impacting factors, leads to a continuous productivity rate of CH4 of 8.5 μmol h−1 g−1 under visible light irradiation over at least 10 h. To the best of knowledge, this level of performance is unprecedented under continuous gas‐phase flowing CO2 in the presence of water as reducing agent, without addition of any sacrificial agent. [ABSTRACT FROM AUTHOR]

The production of reactive oxygen species (ROS), such as hydroxyl radicals, by ultrasonic activation of semiconductor nanoparticles (NPs), including TiO2, has excellent potential for use in sonodynamic therapy and for the sonocatalytic degradation of pollutants. However, TiO2 NPs have limitations including low yields of generated ROS that result from fast electron–hole recombination. In this study, we first investigated the sonocatalytic activity of TiO2-supported Au nanoclusters (NCs) (Au NCs/TiO2) by monitoring the production of hydroxyl radicals (•OH) under ultrasonication conditions. The deposition of Au144 NCs on TiO2 NPs was found to enhance sonocatalytic activity for •OH production by approximately a factor of 2. Electron–hole recombination in ultrasonically excited TiO2 NPs is suppressed by Au144 NCs acting as an electron trap; this charge separation resulted in enhanced •OH production. In contrast, the deposition of Au25 NCs on TiO2 NPs resulted in lower sonocatalytic activity due to less charge separation, which highlights the effectiveness of combining Au144 NCs with TiO2 NPs for enhancing sonocatalytic activity. The sonocatalytic action that forms electron–hole pairs on the Au144/TiO2 catalyst is due to both heat and sonoluminescence from the implosive collapse of cavitation bubbles. Consequently, the ultrasonically excited Au144 (3 wt. %)/TiO2 catalyst exhibited higher catalytic activity for the production of •OH because of less light shadowing effect, in contrast to the lower catalytic activity when irradiated with only external light. [ABSTRACT FROM AUTHOR]

Electron traps generated during the reactive ion etching (RIE) process in n-type 4H-SiC are investigated using the deep-level transient spectroscopy technique and isothermal capacitance transient spectroscopy (ICTS) technique. Two electron traps of the Z1/2 center (E C − 0.64 eV) and the EH3 center (E C − 0.74 eV) are detected in the RIE-etched sample by ICTS measurement at 300 K. A method is proposed to determine the depth profiles of the electron traps that are localized near the etched surface, whereby a depth profile is extracted from the dependence of averaged trap density on the depletion layer width. An exponential distribution is assumed as the depth profile of the electron traps generated during the RIE process. The extracted depth profile was confirmed to be consistent with that determined by the double-correlation method. An appropriate function for the depth profile of carrier traps is assumed and the dependence of the averaged trap density on the depletion layer width is analyzed, which enables the extraction of a depth profile that has both higher depth resolution and higher resolution in the carrier trap density with the proposed method than that with the double-correlation method. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate the radiation detection performance of vertical metal-oxide-semiconductor (MOS) capacitors fabricated on 20 μm thick n-4H-SiC epitaxial layers with the highest energy resolution ever reported. The 100 nm SiO2 layer was achieved on the Si face of n-4H-SiC epilayers using dry oxidation in air. The Ni/SiO2/n-4H-SiC MOS detectors not only demonstrated an excellent energy resolution of 0.42% (Δ E / E × 100) for 5.48 MeV alpha particles but also caused a lower enhancement in the electronic noise components of the spectrometer compared with that observed for the best high-resolution Schottky barrier detectors. The MOS detectors also exhibited a high charge collection efficiency (CCE) of 96% at the optimized operating bias despite the presence of the oxide layer. A drift-diffusion model applied to the CCE vs gate bias voltage data revealed a minority (hole) carrier diffusion length of 24 μm. Capacitance mode deep level transient spectroscopy (C-DLTS) scans in the temperature range 84–800 K were carried out to identify the resolution limiting electrically active defects. Interestingly, the C-DLTS spectra revealed both positive and negative peaks, indicating the simultaneous presence of electron (majority) and hole (minority) trap centers. It has been inferred that at the steady-state bias for the C-DLTS measurement, the MOS detector operates in the inversion mode at certain device temperatures, causing holes to populate the minority trap centers and, hence, manifests minority carrier peaks as well. [ABSTRACT FROM AUTHOR]

The effects of 20 MeV proton irradiation with fluences of 5 × 1014 and 1015 p/cm2 on electrical properties of lightly Sn doped n-type (net donor concentration 3 × 1017 cm−3) bulk β-Ga2O3 samples with (010) and (−201) orientation were studied. Proton irradiation decreases the net donor density with a removal rate close to 200 cm−1 for both orientations and similar to the electron removal rates in lightly Si doped β-Ga2O3 epilayers. The main deep electron traps introduced in the β-Ga2O3 crystals of both orientations are near Ec−0.45 eV, while in Si doped films, the dominant centers were the so-called E2* (Ec−0.75 eV) and E3 (Ec−0.1 eV) traps. Deep acceptor spectra in our bulk –Ga2O3(Sn) crystals were dominated by the well-known centers with an optical ionization energy of near 2.3 eV, often attributed to split Ga vacancies. These deep acceptors are present in a higher concentration and are introduced by protons at a higher rate for the (010) orientation. Another important difference between the two orientations is the introduction in the surface region (∼0.1 μm from the surface) of the (010) of a very high density of deep acceptors with a level near Ec−0.27 eV, not observed in high densities in the (−201) orientation or in Si doped epitaxial layers. The presence of these traps gives rise to a very pronounced hysteresis in the low temperature forward current–voltage characteristics of the (010) samples. These results are yet another indication of a significant impact of the orientation of the β-Ga2O3 crystals on their properties, in this case, after proton irradiation. [ABSTRACT FROM AUTHOR]

Transparent conducting Al -doped ZnO films were grown by atomic layer deposition (ALD). Al -doping was introduced by inserting 1 A l 2 O 3 cycle per 28 ZnO cycles. The x-ray photoelectron spectroscopy showed that the density of the Al donors is 2 × 10 21 – 3 × 10 21 cm − 3 , while the Hall-effect measurements showed a ten times lower electron density. This low doping efficiency is a well-known inherent problem of the ALD method, and we wanted to explain its origin. We have found that the electron density is reduced by electron traps at the grain surface; however, the effect was too weak to explain the low doping efficiency. Therefore, the mechanism of the A l 2 O 3 doping was analyzed. We have proposed that each A l 2 O 3 molecule ideally provides two single-electron Al donors accompanied by one Zn vacancy, which acts as a two-electron acceptor. This would cause a perfect compensation; however, the compensation is in reality not perfect, which results in weakly efficient doping. Calculations also showed that each Zn vacancy creates a bound pair with an Al donor. To verify our doping model experimentally, it was inserted into the metallic transport theory and compared with the electron transport measurements. A good agreement was found for a broad range of experimental conditions. In the regime of weak localization, the conductivity showed the temperature dependence σ (T) = a + b T 3 / 4 , which is a signature of weak localization and electron–electron scattering in a 3D dirty metal. [ABSTRACT FROM AUTHOR]

A quasi-equilibrium (QE) theoretical model is proposed to fit the slow dispersive electron relaxation of nano-TiO2 that occurs through the transfer to O2. The electron relaxation is obtained from measurement of photoinduced absorptions. By including both the traps with exponential and Gaussian distributions with respect to the energy, the electron relaxation is fully fitted with the QE model. A Monte Carlo simulation is also realized to fit the electron relaxation, which agrees well with the QE model. It is revealed that the kinetics of the electron transfer from TiO2 to O2 contains both contributions from the exponential and Gaussian traps. Their distributions are obtained from the QE model fitting. The dispersion factor of the exponential traps is ∼0.65 and the trap density is high. The Gaussian traps locate ∼0.4 eV below the conduction band and have narrow distribution. The density of the Gaussian traps is more than three orders of magnitude lower than that of the exponential traps. Despite the low density, the Gaussian traps have an important effect on the electron relaxation. The distributions of the thermal barriers for the electron relaxation are obtained for both relaxations contributed by the exponential and Gaussian traps, based on which the kinetics equations are proposed. The Gaussian trap contributed relaxation accords with mono-exponential kinetics, while the relaxation contributed from the exponential traps involves exponentially distributed weights. The apparent activation energy, kinetic time constants, and pre-exponential factor can be obtained. [ABSTRACT FROM AUTHOR]

In this study, high-resistivity gold-implanted silicon substrates developed for radio frequency (RF) applications were characterized. By varying PICTS (Photo-Induced Current Transient Spectroscopy) measurement conditions such as the illumination wavelength, we identified the signature and the nature of four dominant traps. Two were electron traps and the others were hole traps. All of the related defects involved gold atoms. RF simulations of coplanar waveguide transmission lines integrated on these substrates were carried out, based on the trap properties extracted from PICTS results. A good agreement between RF experimental data and simulations was achieved by tuning the trap concentrations. Finally, the gold density extracted from the fit was successfully compared with the secondary ion mass spectrometry profile and an explanation of the role of the traps in RF behavior of the substrate was given. [ABSTRACT FROM AUTHOR]

The 2D electrons trapped in vacuum near the atomically thin dielectric (ATD, mono- or N -layer film of h -BN or transition metal dichalcogenide) are considered. ATD is suspended above the back gate and forms the capacitor, which is controlled by the biased voltage determining 2D concentration, n 2 D . It is found that the leakage current through ATD is negligible, and the effect of the polarizability of ATD is weak if N ≤ 5. At temperatures T = 0.1 – 15 K and n 2 D = 5 × 10 8 – 10 10 cm − 2 , one deals with the Boltzmann liquid having a macroscopic thickness of ∼ 100 A. Due to the bending of ATD, the quadratic dispersion law of the flexural vibrations is transformed into the linear one at small wave vectors. The scattering processes of the electrons caused by these phonons or the monolayer islands on ATD are examined and the momentum and energy relaxation rates are analyzed based on the corresponding balance equations. The momentum relaxation times vary over orders of magnitude in the above region (T , n 2 D ) and N. The response may change from the polaron transport, for a perfect single-layer ATD at low T and high n 2 D , to the high-mobility (≥ 10 7 cm 2 / V s) regime at high T and low n 2 D . The quasi-elastic energy relaxation due to phonon-induced scattering is considered, and the conditions for the heating of electrons by a weak in-plane electric field are found. [ABSTRACT FROM AUTHOR]

Films of Ga2O3 were grown by Halide Vapor Phase Epitaxy (HVPE) on bulk heavily B-doped (001)-oriented diamond substrates using thin interlayers of Al2O3 deposited by HVPE or AlN/AlGaN deposited by metalorganic chemical vapor deposition. The growth with AlN/AlGaN was dominated by the formation of a highly conducting ɛ-phase with poor crystalline quality. For these samples, excessive leakage of Schottky diodes and of the Ga2O3/diamond heterojunction prevented meaningful electrical characterization. The film grown with the Al2O3 interlayer was mainly composed of (−201) β-Ga2O3 with an admixture of the ɛ-phase. The film had a low density of residual shallow donors, 5 × 1015 cm−3, with deep electron traps spectra consisting of the well documented centers for β-Ga2O3 near Ec 0.27, Ec 0.7, and Ec 1 eV, all of which are often ascribed to native defects or their complexes. The electrical properties of heterojunctions were mostly determined by the properties of the Ga2O3 films. Both Schottky diodes and heterojunctions showed measurable photosensitivity for 259 nm wavelength excitation, but very low photocurrent for near-UV (365 nm wavelength excitation). [ABSTRACT FROM AUTHOR]