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Flexible PbZr0.52Ti0.48O3 (PZT) films have a wide application prospect in wearable devices. In this work, PZT films were fabricated on LaNiO3–based Si substrates and mica substrates, respectively. The effects of Si substrates and mica substrates on the dielectric and ferroelectric properties of PZT films were studied. The stability of PZT films on different substrates was discussed by controlling temperature and frequency. The optimal annealing temperature for preparing PZT films on LaNiO3–based Si substrates and mica substrates is 750 °C. The dielectric and ferroelectric properties of PZT films vary with the substrates. The diffraction peak of PZT films deposited on mica substrates shifted to the left compared with that deposited on Si substrates, due to difference of the expansion coefficients. The as–prepared PZT films exhibit a good ferroelectric property at a frequency in the range of 100 Hz~1000 Hz. Moreover, PZT films deposited on mica substrates have larger remanent polarization values and coercive fields than PZT films deposited on Si substrates. With the elevation in temperature, the dielectric constant of PZT films gradually enhance. And as–prepared PZT films at an annealing temperature of 750 °C have a better dielectric temperature stability. PZT films grown on Si substrates exhibit more excellent dielectric temperature stability than that of PZT films grown on mica substrates. [ABSTRACT FROM AUTHOR]

In this study, Piezoelectric energy harvesters (PEHs) are fabricated based on epitaxial Pb(Zr,Ti)O3 (PZT) thin films deposited by an RF magnetron sputtering with varied Zr/[Zr+Ti] ratio. For a compatibility with micro‐electromechanical systems, the epitaxial PZT thin films are deposited on Si substrates (PZT/Si). The morphotropic phase boundary (MPB) are formed in the compositional range of 0.44 ≤ Zr/[Zr+Ti] ≤ 0.51 of the epitaxial PZT/Si, which is far broader than that of the bulk PZT. Meanwhile, effective transverse piezoelectric coefficient (|e31,f|) values are evaluated by the direct and converse piezoelectric effects using the unimorph cantilever method. Among the compositions, the rhombohedral‐dominant MPB (MPB‐R) of Zr/[Zr+Ti] = 0.51 exhibits a direct |e31,f| of 10.1 C m−2 and a relative permittivity (εr) of 285, leading to the maximum figure of merit of 40 GPa in this study. On the other hand, the maximum converse |e31,f| of 14.0 C m−2 is measured from the tetragonal‐dominant MPB (MPB‐T) of Zr/[Zr+Ti] = 0.44. At a resonance frequency, the MPB‐T presents a high output power density of 301.5 µW−1/(cm2 g2) under an acceleration of 3 m−1 s−2, which is very promising for the high‐performance PEH applications. [ABSTRACT FROM AUTHOR]

Abstract In this study, Piezoelectric energy harvesters (PEHs) are fabricated based on epitaxial Pb(Zr,Ti)O3 (PZT) thin films deposited by an RF magnetron sputtering with varied Zr/[Zr+Ti] ratio. For a compatibility with micro‐electromechanical systems, the epitaxial PZT thin films are deposited on Si substrates (PZT/Si). The morphotropic phase boundary (MPB) are formed in the compositional range of 0.44 ≤ Zr/[Zr+Ti] ≤ 0.51 of the epitaxial PZT/Si, which is far broader than that of the bulk PZT. Meanwhile, effective transverse piezoelectric coefficient (|e31,f|) values are evaluated by the direct and converse piezoelectric effects using the unimorph cantilever method. Among the compositions, the rhombohedral‐dominant MPB (MPB‐R) of Zr/[Zr+Ti] = 0.51 exhibits a direct |e31,f| of 10.1 C m−2 and a relative permittivity (εr) of 285, leading to the maximum figure of merit of 40 GPa in this study. On the other hand, the maximum converse |e31,f| of 14.0 C m−2 is measured from the tetragonal‐dominant MPB (MPB‐T) of Zr/[Zr+Ti] = 0.44. At a resonance frequency, the MPB‐T presents a high output power density of 301.5 µW−1/(cm2 g2) under an acceleration of 3 m−1 s−2, which is very promising for the high‐performance PEH applications.

We studied the effectiveness of post-growth patterning and annealing on threading dislocation (TD) reduction in (211) CdTe/Si epilayers grown using metalorganic vapor-phase epitaxy (MOVPE). Sixty-micrometer-wide square patterns were formed on the as-grown CdTe samples using photolithography and then subjected to ex situ annealing in a flowing hydrogen environment. The annealing temperature was varied from 550°C to 800°C, then held at this temperature for a fixed duration of 5 min. The TD densities were determined using the etch pit density (EPD) technique. A comparison of EPD values revealed that the patterned samples had lower EPD values than the unpatterned samples annealed under similar conditions. This suggests that annealing promotes dislocation glide to the sidewalls of the islands and is thus more effective at dislocation removal for the patterned samples in comparison to the unpatterned samples. [ABSTRACT FROM AUTHOR]

Herein, the AlGaN/GaN high‐electron‐mobility transistors (HEMTs) on silicon substrates using thick copper‐metallized interconnects with Pt diffusion barrier layer for Ka‐band application are reported. High output power density of 6.6 W mm−1 with power‐added efficiency (PAE) of 45.6% at 28 GHz is achieved for the 4 × 50 μm device in continuous‐wave (CW) mode. No obvious change in the drain–source current (IDS) is observed for the device under 40 V high‐voltage stress for 100 h and the device shows good thermal stability when annealed at 300 °C for 30 min. It demonstrates that the AlGaN/GaN HEMTs on silicon substrate with thick copper‐metallized interconnects can enhance the device performance with good reliability for future 5 G applications. [ABSTRACT FROM AUTHOR]

DLC films were deposited on Si substrates using direct ion beam deposition method, followed by investigating the influence of O2 and N2 doping on their electrical and structural properties. The films were doped with oxygen and nitrogen under flow rates of 5 and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy. Result showed that by increasing oxygen incorporation, sp2 content decreases, sp3 content increases, and the C-C bonding loses its order. As the size of the sp2-rich cluster increased with N2 content, the disorder in the DLC samples decreased, leading to a decrease in the FWHM of the G peak. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°. With increasing nitrogen flow rate from 5 to 40, the contact angle of DLC thin films increased from 78° to 110°.

Mica nanolayers (MNL) are a new dielectric material that can improve the electron transport properties of Si based microelectronic devices. However, the mechanical reliability of such devices is not well understood because measurement of the adhesion between an MNL and a Si substrate is insufficiently accurate. The recent work reports a bridging method that is developed based on the linear beam theory and can characterize the adhesion of MNL on a mica substrate in a reasonably accuracy. In this work, the accuracy of the bridging method is improved by using a nonlinear mechanical model. 15 MNL specimens are measured on a Si substrate in air and the new model gives an average adhesion energy of 119.69 ± 20.47 mJ m–2. The effect of environment on the adhesion is also investigated. The increase in temperature from 25 to 300 °C enhances adhesion, attributed to the increased bonding effect of interfacial contaminants. When humidity is below a threshold value, 80% in this case, the adhesion energy remains unchanged, but above the threshold, the nanobridges collapse during testing. Molecular dynamics simulation reveal that the collapse is because the increase of interfacial water molecules reduces the frictional force between the MNL and Si substrate. [ABSTRACT FROM AUTHOR]

As the key device in a UV warning system, a solid‐state UV photodetector has attracted great attention. Herein, a new UV photodetector structure based on vertical (Al, Ga)N nanowires with graphene electrode and Si substrate is designed and demonstrated. By graphene/vertical (Al, Ga)N nanowire array heterojunction, the rectifying characteristics of I–V curve are formed, and the dark current is 54 nA at −2 V bias. The fabricated device exhibits a responsivity of 0.176 mA W−1 at the bias of −2 V, as well as a stable switching characteristic. It is proposed that the photogenerated electrons and holes can reach positive and negative electrodes by diffusion or tunneling effect, even with thick AlN sections. This method can promote the implementation of low cost for UV photodetector with adjustable detection range nowadays. [ABSTRACT FROM AUTHOR]

Core–shell GaAs-based nanowires monolithically integrated on Si constitute a promising class of nanostructures that could enable light emitters for fast inter- and intrachip optical connections. We introduce and fabricate a coaxial GaAs/(In,Ga)As dot-in-a-well nanowire heterostructure to reach spontaneous emission in the Si transparent region, which is crucial for applications in Si photonics. Specifically, we achieve room temperature emission at 1.27 μm in the telecommunication O band. The presence of quantum dots in the heterostructure is evidenced by a structural analysis based on scanning transmission electron microscopy. The spontaneous emission of these nanowire structures is investigated by cathodoluminescence and photoluminescence spectroscopy. Thermal redistribution of charge carriers to larger quantum dots explains the long wavelength emission achieved at room temperature. Finally, to demonstrate the feasibility of the presented nanowire heterostructures as electrically driven light emitters monolithically integrated on Si, a light-emitting diode is fabricated exhibiting room-temperature electroluminescence at 1.26 μm. [ABSTRACT FROM AUTHOR]

Preparation of ordered CoPt on Si substrates is significant for expanding future applications of spintronic devices. In this study, ordered CoPt alloys including the L 1 _0 phase with a maximum coercivity of 2.1 kOe are formed in electron-beam-deposited 11.4 nm thick Pt/Co bilayer thin films on Si/SiO _2 substrates via interdiffusion during rapid thermal annealing (RTA). The effects of RTA temperature on the magnetic properties, crystal structures, cross-sectional elemental profiles, and surface morphologies of the films are analyzed by vibrating sample magnetometer (VSM), grazing incidence x-ray diffraction (GI-XRD), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscope (SEM), respectively. For the as-deposited film, polycrystalline Pt was confirmed by uniform Debye–Scherrer rings of Pt. At 200 °C, interdiffusion between Co and Pt atoms in the film started to be observed by EDX elemental maps, and at 300 °C, alloying of Co and Pt atoms was confirmed by diffraction peaks corresponding to A 1-disordered CoPt. At 400 °C, the in-plane coercivity of the film began to increase. At 700 °C, ordered CoPt alloys were confirmed by superlattice diffraction peaks. At 800 °C, a graded film containing L 1 _0 -ordered CoPt was found to be formed and a maximum coercivity of 2.1 kOe was observed by VSM, where the easy axis of magnetization was oriented along the in-plane direction. At 900 °C, deformation of the ordered CoPt alloys was observed by GI-XRD, and the grain size of the film reached a maximum.

Ex situ low-temperature (LT)-AlN templates are employed to realize GaN-based light-emitting diodes (LEDs) on Si substrates by the combination of pulsed laser deposition and metal organic chemical vapor deposition. The influence of ex situ LT-AlN template thickness on the properties and performance of as-grown LEDs has been carefully studied. The LED wafer grown on 70-nm-thick ex situ LT-AlN template exhibits a crack-free surface, good crystalline quality, and excellent multiple quantum wells (MQWs) structural property. The 500 × 500 μm2 LED chips fabricated with lateral structure show the highest light output power of 70.2 mW at an injection current of 300 mA. Through optimizing the thickness of ex situ LT-AlN template, the light output power is greatly improved by 39%. Theoretical analysis has been taken to study the enhancement mechanism of luminous intensity in this LED. It reveals that the residual stress in as-grown wafers is significant to enhance the luminescence of LEDs. The largest residual tensile stress in the LED presents great potential to enhance the carrier injection and transportation, increase the carrier concentrations, and improve the radiative recombination intensity in MQWs, which is crucial to improve the luminous intensity of LEDs. [ABSTRACT FROM PUBLISHER]

Three kinds of ex situ low-temperature AlN (LT-AlN) templates grown on Si substrates by pulsed laser deposition (PLD) are employed to grow GaN epitaxial films by metal organic chemical vapor deposition (MOCVD). The single-crystalline ex situ LT-AlN template with smooth surface shows the greatest advantage to achieve high-quality GaN epitaxial films. It can effectively promote the lateral growth of high-temperature AlN layer to obtain coalesced and smooth surface, and therefore reduce the GaN nucleation energy barrier to facilitate GaN nucleation process. The as-grown truncated GaN nuclei with large sizes and low density are favorable for the two-dimensional growth of GaN. The ∼1.5 μm-thick GaN epitaxial film grown on this ex situ LT-AlN template shows a flat surface and the best crystalline quality with the minimum full-width at half maximums (FWHMs) of GaN(0002) and GaN(10–12) X-ray rocking curves (XRCs) as 504 and 566 arcsec, respectively, and the minimum FWHM of near band emission peak as 20.62 nm. According to the XRC results, compared with the GaN film grown without ex situ LT-AlN templates, the screw-type threading dislocations (TDs) density, edge- and mixed-type TDs density in as-grown GaN film are greatly reduced by 20% and 49%, respectively, proving the superiority of ex situ LT-AlN template. This work is instructional for the growth of high-quality nitride films by combination methods, and significant for achieving high-performance GaN-based devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au nanowires grow by thermal evaporation on the Si substrate irradiated with Ar+. • Using this methods, freestanding Au nanowires with high aspect ratios are fabricated. • Nanowires grow only at the boundary of the ion-irradiated and unirradiated regions. • Patterning the Si substrate during ion irradiation increase the number of nanowires. • Such nanowires are single crystals and grow along the [1 1 0] direction. We demonstrated the site-selective growth of freestanding single-crystalline Au NWs at a low temperature (approximately 573 K) by pretreating a silicon substrate with low-energy ion beams, followed by thermal evaporation of Au. Using this method, Au NWs with aspect ratios up to 1000 or more, that is, 50–200 nm in diameter and lengths ranging from several hundred nanometers to approximately 100 μm, were fabricated. Au NWs could only be grown at the boundary between the ion-irradiated and unirradiated regions on the Si substrates during the deposition of Au. Furthermore, patterning the Si substrate by masking it with a fine mesh during ion irradiation creates more boundaries between the irradiated and unirradiated regions, increasing the number of Au NWs. Transmission electron microscopy and selected-area electron diffraction revealed that the NWs were single crystals and grew along the [1 1 0] direction. [ABSTRACT FROM AUTHOR]

Yttrium Iron Garnet (YIG) films were prepared on Si substrates by Chemical Solution Deposition (CSD) technique using acetic acid and deionized water as solvents. Well-crystallized and crack-free YIG films were obtained when annealed at 750 °C and 850 °C respectively, showing a low surface roughness of several nanometers. When annealed at 750 °C for 30 min, the saturated magnetization (Ms) and coercive field (Hc) of YIG films were 0.121 emu/mm 3 (4πMs = 1.52 kGs) and 7 Oe respectively, which were similar to that prepared by PLD technique. The peak-to-peak linewidth of ferromagnetic resonance (FMR) was 220 Oe at 9.10 GHz. The results demonstrated that CSD was an excellent technique to prepare high quality yttrium iron garnet (YIG) films on silicon, which could provide a lower-cost way for large-scale production on Si-based integrated devices. [ABSTRACT FROM AUTHOR]

In this work, a series of NWs growths with different treatments for substrate surface have been carried out to study growth morphology optimization for NWs grown on Si substrates. A substrate treatment method of high-temperature annealing combined with thin oxide layer formed on the substrate surface has been developed. It is found that a lot of crystal defects exist in random locations of common substrates surface which make it difficult to grow NWs, but easy to form parasitic islands. XRD and AFM show that high-temperature annealing process can effectively eliminate most of the crystal defects in the substrates, inhibit the formation of parasitic islands. Combined with forming thin natural oxide layer on the substrate surface, the density of InAs NWs can be increased, the growth morphology uniformity of InAs NWs on Si substrates can be improved and parasitic islands are rarely formed on the substrates surface at all. In order to verify the effectiveness and universality of this method, another experiment of InGaAs NWs grown at different temperatures obtained excellent growth results as well. Therefore, this substrate treatment method has good effectiveness, repeatability and universality in optimizing the growth morphology of NWs. • Lots of crystal defects exist in Si substrates which make it difficult to grow NWs, but easy to form parasitic islands. • A substrate treatment method can effectively improve the growth of NWs and inhibit the parasitic islands. • This substrate treatment method has good effectiveness, repeatability and universality in optimization of NWs. [ABSTRACT FROM AUTHOR]

Perovskite-spinel epitaxial nanocomposite thin films are commonly grown on single crystal perovskite substrates, but integration onto a Si substrate can greatly increase their usefulness in devices. Epitaxial BiFeO3-CoFe2O4 nanocomposites consisting of CoFe2O4 pillars in a BiFeO3 matrix are grown on (001) Si with two types of buffer layers: molecular beam epitaxy (MBE)-grown SrTiO3-coated Si and pulsed-laser-deposited (PLD) Sr(Ti0.65Fe0.35)O3/CeO2/yttria-stabilized ZrO2/Si. The nanocomposite grows with the same crystallographic orientation and morphology as that observed on single crystal SrTiO3 when the buffered Si substrates are smooth, but roughness of the Sr(Ti0.65Fe0.35)O3 promoted additional CoFe2O4 pillar orientations with 45° rotation. The nanocomposites on MBE-buffered Si show very high magnetic anisotropy resulting from magnetoelastic effects, whereas the hysteresis of nanocomposites on PLD-buffered Si can be understood as a combination of the hysteresis of the Sr(Ti0.65Fe0.35)O3 film and the CoFe2O4 pillars. [ABSTRACT FROM AUTHOR]

Mercury cadmium telluride (HgCdTe) grown on large-area silicon (Si) substrates allows for larger array formats and potentially reduced focal-plane array (FPA) cost compared with smaller, more expensive cadmium zinc telluride (CdZnTe) substrates. In this work, the use of HgCdTe/Si for mid- wavelength/long-wavelength infrared (M/LWIR) dual-band FPAs is evaluated for tactical applications. A number of M/LWIR dual-band HgCdTe triple-layer n- P- n heterojunction device structures were grown by molecular-beam epitaxy (MBE) on 100-mm (211)Si substrates. Wafers exhibited low macrodefect densities (< 300 cm). Die from these wafers were mated to dual-band readout integrated circuits to produce FPAs. The measured 81-K cutoff wavelengths were 5.1 μm for band 1 (MWIR) and 9.6 μm for band 2 (LWIR). The FPAs exhibited high pixel operability in each band with noise-equivalent differential temperature operability of 99.98% for the MWIR band and 98.7% for the LWIR band at 81 K. The results from this series are compared with M/LWIR FPAs from 2009 to address possible methods for improvement. Results obtained in this work suggest that MBE growth defects and dislocations present in devices are not the limiting factor for detector operability, with regards to infrared detection for tactical applications. [ABSTRACT FROM AUTHOR]

Abstract: InGaN/GaN multiple-quantum-well solar cells were grown on (111) Si substrates. AlN/AlGaN superlattice and self-assembly Si x N y masking islands were employed to alleviate the material mismatches between Si and GaN. The devices were characterized under the illumination of AM 1.5G with different solar concentrations. As the concentration ratios increased from 1-sun to 105-sun, energy conversion efficiency was enhanced by 25%, which was noticeably greater than the enhancement reported on sapphire substrates under similar solar concentrations. The result is attributed to the superior heat sinking of Si substrates. [Copyright &y& Elsevier]

HgCdTe grown on large-area Si substrates allows for larger array formats and potentially reduced focal-plane array (FPA) cost compared with smaller, more expensive CdZnTe substrates. The goal of this work is to evaluate the use of HgCdTe/Si for mid-wavelength/long-wavelength infrared (MWIR/LWIR) dual-band FPAs. A series of MWIR/LWIR dual-band HgCdTe triple-layer n- P- n heterojunction (TLHJ) device structures were grown by molecular-beam epitaxy (MBE) on 100-mm (211)Si substrates. The wafers showed low macrodefect density (<300 cm) and was processed into 20- μm-unit-cell 640 × 480 detector arrays which were mated to dual-band readout integrated circuits (ROICs) to produce FPAs. The measured 80-K cutoff wavelengths were 5.5 μm for MWIR and 9.4 μm for LWIR, respectively. The FPAs exhibited high pixel operabilities in each band, with noise equivalent differential temperature (NEDT) operabilities of 99.98% for the MWIR band and 99.6% for the LWIR band demonstrated at 84 K. [ABSTRACT FROM AUTHOR]

Electrical properties of halogen-doped CdTe layers grown on Si substrates using iodine and chlorine dopants are presented. No change in electrical properties of the layers was observed with chlorine as a dopant. However, doping with iodine resulted in highly conductive n-type layers or highly resistive p-type layers depending upon the growth conditions, even though a similar amount of dopant was introduced into the growth chamber. Layers grown at 560°C, with a vapor-phase Te/Cd precursor ratio of 3.0, were p-type. The resistivity of the layers remained unchanged for low dopant supply rates, but increased abruptly when the dopant supply rate was increased beyond a certain value. On the other hand, layers grown at 325°C with Te/Cd ratios from 0.1 to 0.25 were n-type. A maximum free electron concentration of 1.3 × 1017 cm−3 was obtained at room temperature. The types and conductivities of the grown layers were strongly dependent on the growth conditions. [ABSTRACT FROM AUTHOR]

n‐InAs/p‐GaSb Esaki diodes with 3 nm GaSb i‐layers are fabricated on Si and GaSb substrates. The on Si sample devices exhibit lower peak to valley ratios and peak current density than their on GaSb counterparts at 3.27 against 4.45 and 119 against 336 kA/cm2, respectively. The findings are similar to other reports of integrating III–V Esaki diodes onto Si. [ABSTRACT FROM AUTHOR]

In this paper, we have fabricated InGaAs high-electron-mobility transistors (HEMTs) on Si substrates. The InAlAs/InGaAs heterostructures were initially grown on InP substrates by molecular beam epitaxy (MBE), and the adhesive wafer bonding technique was employed to bond the InP substrates to Si substrates, thereby forming high-quality InGaAs channel on Si. The 120 nm gate length device shows a maximum drain current (I D , m a x ) of 569 mA/mm, and the maximum extrinsic transconductance (g m , m a x ) of 1112 mS/mm. The current gain cutoff frequency (f T ) is as high as 273 GHz and the maximum oscillation frequency (f M A X ) reaches 290 GHz. To the best of our knowledge, the g m , m a x and the f T of our device are the highest ever reported in InGaAs channel HEMTs on Si substrates at given gate length above 100 nm. [ABSTRACT FROM AUTHOR]

Abstract: Based on electron-beam direct writing on the SiO x /Si substrates, favorable absorption sites for ferric cations (Fe3+ ions) were created on the surface oxide layer. This allowed Fe3+-assisted self-assembled arrays of single-wall carbon nanotube (SWNT) probes to be produced. Auger investigation indicated that the incident energetic electrons depleted oxygen, creating more dangling bonds around Si atoms at the surface of the SiO x layer. This resulted in a distinct difference in the friction forces from unexposed regions as measured by lateral force microscopy (LFM). Atomic force microscopy (AFM) affirmed that the irradiated domains absorbed considerably more Fe3+ ions upon immersion into pH 2.2 aqueous FeCl3 solution. This rendered a greater yield of FeO(OH)/FeOCl precipitates, primarily FeO(OH), upon subsequent washing with lightly basic dimethylformamide (DMF) solution. Such selective metal-functionalization established the basis for the subsequent patterned forest-assembly of SWNTs as demonstrated by resonance Raman spectroscopy. [Copyright &y& Elsevier]

We describe the epitaxial growth of InSb films on both Si (001) and GaAs (100) substrates using molecular-beam epitaxy and discuss the structural and electrical properties of the resulting films. The complete 2 μm InSb films on GaAs (001) were grown at temperatures between 340°C and 420°C and with an Sb/In flux ratio of approximately 5 and a growth rate of 0.2 nm/s. The films were characterized in terms of background electron concentration, mobility, and x-ray rocking curve width. Our best results were for a growth temperature of 350°C, resulting in room-temperature mobility of 41,000 cm2/V s. For the growth of InSb on Si, vicinal Si(001) substrates offcut by 4° toward (110) were used. We investigated growth temperatures between 340°C and 430°C for growth on Si(001). In contrast to growth on GaAs, the best results were achieved at the high end of the range of T S = C, resulting in a mobility of 26,100 cm2/V s for a 2 μm film. We also studied the growth and properties of InSb:Mn films on GaAs with Mn content below 1%. Our results showed the presence of ferromagnetic ordering in the samples, opening a new direction in the diluted magnetic semiconductors. [ABSTRACT FROM AUTHOR]

Abstract: We report the investigation of morphology and composition of copper nanocluster films deposited on Si substrates. The nanoclusters are formed in an aggregation tube at room temperature and magnetron sputtering source is used to get negatively charged Cu-clusters'' beam which is subsequently mass-filtered to get size-selected cluster on the substrates as soft-landing process of deposition. For composition of the films, X-ray photoelectron spectroscopy (XPS) technique is used. For morphological changes of the films both scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses are carried out. Additionally, Energy Dispersive X-ray (EDX) spectra support the compositional and structural informations of the film. The analysis of Cu nanoclusters'' films reveals that initial nucleation of Cu clusters takes place in the form of isolated islands and the arrival of subsequent Cu clusters onto Si substrates has preferential aggregation around the preceding clusters forming a mound structure. [Copyright &y& Elsevier]

We report on the growth of very thick (>260 µm) high-crystalline-quality single-crystal CdTe epitaxial films on (211) Si substrates in a metalorganic vapor-phase epitaxy reactor, and the development of gamma ray detectors and their radiation detection properties. Films were grown with a high growth rate varying from 40 µm/h to 70 µm/h. A heterojunction diode was fabricated by growing a 90-µm-thick CdTe layer on an n+-Si substrate, which exhibited good rectifying behavior and had a low reverse bias leakage current of 0.18 µA/cm² at 100 V bias. The diode clearly demonstrated its gamma radiation detection capability by resolving energy peaks from the 241Am radioisotope during room-temperature measurements. By cooling the diode detector to -30°C, the leakage current could be reduced by three orders of magnitude from the room-temperature value. At this operating condition dramatic improvements in the pulse height spectrum were observed. [ABSTRACT FROM AUTHOR]

Abstract: AlGaN ultraviolet metal-semiconductor-metal photodetectors (PDs) with low temperature (LT)-AlN and LT-GaN cap layers were prepared on Si substrates. Unlike PDs prepared on sapphire substrates, no markedly reduction in dark current was observed from the PD with LT-GaN cap layer. With an incident wavelength of 305nm and an applied bias of 5V, it was found that peak responsivities were 0.02, 0.005 and 0.007A/W for the PDs with LT-AlN cap layer, with LT-GaN cap layer and without cap layer, respectively. The corresponding detectivities were 2.2×1010, 1.36×1010 and 1.55×1010 cmHz0.5 W−1, respectively. [Copyright &y& Elsevier]

We have studied the evolution of threading dislocations (TDs), stress, and cracking of GaN films grown on (111) Si substrates using a variety of buffer layers including thin AlN, compositionally graded AlxGa1-xN (0 ≤ x ≤ 1), and AlN/AlyGa1-yN/AlxGa1-xN (0 ≤ x ≤ 1, y = 0 and 0.25) multilayer buffers. We find a reduction in TD density in GaN films grown on graded AlxGa1-xN buffer layers, in comparison with those grown directly on a thin AlN buffer layer. Threading dislocation bending and annihilation occurs in the region in the graded AlxGa1-xN grown under a compressive stress, which leads to a decrease of TD density in the overgrown GaN films. In addition, growing a thin AlN/ AlyGa1-yN bilayer prior to growing the compositionally graded AlxGa1-xN buffer layer significantly reduces the initial TD density in the AlxGa1-xN buffer layer, which subsequently further reduces the TD density in the overgrown GaN film. In-situ stress measurements reveal a delayed compressive-to-tensile stress transition for GaN films grown on graded AlxGa1-xN buffer layers or multilayer buffers, in comparison to the film grown on a thin AlN buffer layer, which subsequently reduces the crack densities in the films. [ABSTRACT FROM AUTHOR]

The use of silicon as a substrate alternative to bulk CdZnTe for epitaxial growth of HgCdTe for infrared (IR) detector applications is attractive because of potential cost savings as a result of the large available sizes and the relatively low cost of silicon substrates. However, the potential benefits of silicon as a substrate have been difficult to realize because of the technical challenges of growing low defect density HgCdTe on silicon where the lattice mismatch is ∼19%. This is especially true for LWIR HgCdTe detectors where the performance can be limited by the high (∼5 x 106 cm-2) dislocation density typically found in HgCdTe grown on silicon. We have fabricated a series of long wavelength infrared (LWIR) HgCdTe diodes and several LW!R focal plane arrays (FPAs) with HgCdTe grown on silicon substrates using MBE grown CdTe and CdSeTe buffer layers. The detector arrays were fabricated using Rockwell Scientific's planar diode architecture. The diode and FPA and results at 78 K will be discussed in terms of the high dislocation density (∼5 x 106 cm²) typically measured when HgCdTe is grown on silicon substrates. [ABSTRACT FROM AUTHOR]

First prototypes of electrooptic (EO) planar deflector switches (PDSs) are fabricated with hybrid integration on Si substrates. Planar optical modules, made in silica-on-silicon technology, consist of input and output (I/O) waveguide microlenses facing each other and slab waveguides in between. The modules interconnect the I/O fibers with laterally collimated light beams less than 400 μm in width at distances up to 100 mm with losses lower than 3 dB. Thin lead lanthanum zirconium titanate (PLZT) films with prism-shaped electrodes grown on SrTiO3 substrates form the deflector elements. The PLZT films are more than 10 μm thick with EO coefficients about 40 pm/V. The deflector assembly technology provides chip vertical positioning accuracy better than 1 μm. The deflector chips are attached to the optical substrates with thermo-compression flip-chip bonding. The optical power losses of the modules with test silica chips can be as low as 3.6 dB. However, the lowest module losses achieved with PLZT are about 10 dB. The channel-to-channel switching operations are demonstrated at about 40 V and switching times less than 500 ns. [ABSTRACT FROM PUBLISHER]

Ordered arrays of Au nanoclusters have been prepared on Si substrates using a combination of focused ion beam (FIB) surface processing and electroless deposition. Particles varying in size from approximately 30 to 100 nm have been produced in regular grid patterns whose geometry is controlled to high precision by the FIB. Potential applications range from engineering of the surface plasmon resonance for numerous optical applications to building structures for tethering organic molecules in specific geometric arrangements. [ABSTRACT FROM PUBLISHER]

The optical, photoluminescent (PL), and electroluminescent (EL) properties of Zn2Si0.5Ge0.5O4:Mn (ZSG:Mn) have been studied in order to determine its viability as a light source for integrated optics systems. ZSG:Mn thin films were deposited at room temperature by RF-sputtering on Si substrates. EL devices (ELDs) were fabricated using transparent indium-tin oxide electrodes. ELDs using as-deposited ZSG:Mn films emitted bright orange light with a broad spectrum at 590-660 nm. Annealing at 700°C resulted in a color shift to green emission in a band from 510 to 550 nm and peaking at 520 nm. Ridge waveguides fabricated by induction-coupled plasma etching yielded an optical loss of 3.8 dB/cm at 633 nm. Prism coupling experiments revealed a decrease in the film refractive index as the result of the anneal. The combination of strong PL, EL, and low waveguide loss demonstrates the strong potential of transition metal- and/or rare-earth-doped ZSG as a robust light source for integrated optic systems. [ABSTRACT FROM PUBLISHER]

The etch rates and mechanisms for HfO2 thin films in Cl2-, SF6- or CH4/H2-based plasmas were measured as a function of source power, r.f. chuck power and discharge composition. Both Cl2- and SF6-based plasmas produced some degree of chemical enhancement in the etch mechanism. Selectivities between 0.2 and 5 were obtained for Si over HfO2 in these two plasma chemistries. High fidelity pattern transfer was achieved for photoresist-masked HfO2/Si structures etched with Cl2/Ar over a broad range of pressures or with SF6/Ar at low pressures. The surface morphologies of both HfO2 and Si were smooth over a wide range of etching conditions. [Copyright &y& Elsevier]

In this paper, the design and fabrication of silicon-based optical waveguides are revisited. The goal is to develop a novel design and deposition process to minimize leakage losses. Interface roughness and Si3N4 stoichiometry are examined. The optical loss is measured and contributions from scattering and absorption are determined [ABSTRACT FROM PUBLISHER]

A nano-robotic manipulation system using an atomic force microscope probe as the pushing manipulator and force and topology sensor is proposed. The task is the two-dimensional positioning of nanometer-size particles on a substrate in ambient conditions. Thus, the modeling of interaction forces and dynamics during the pushing operation is analyzed, and compared with the experimental results for an improved understanding of the nano scale physical phenomenon which is different from macro scale physics. Simulations and experiments are held for determining the conditions and strategies for reliable manipulation, and determining the affecting parameters. The results show that the latex particles with 242- and 484-nm radii can be positioned on Si substrates successfully with around 30-nm accuracy, and the behavior of the particle motion during pushing can be predicted from the experimental data [ABSTRACT FROM PUBLISHER]

The technique of spectroscopic ellipsometry (SE) has been utilized to monitor in real-time and precisely control the surface temperature of Hg1−xCdxTe during molecular beam epitaxy. Due to the temperature dependence of the Hg sticking coefficient under Hg-deficient growth conditions, the near-surface composition of an epilayer is extremely sensitive to surface temperature. SE data were acquired in real time and modeled using a previously established library of dielectric functions of Hg1−xCdxTe as a function of composition. Utilizing SE-generated compositional profiles as a guide, substrate heating power was adjusted in such a way as to minimize composition transients. To demonstrate the effectiveness of the technique, we have used SE to control the temperature of HgCdTe epilayer surfaces during deposition on three-inch (211)CdZnTe/ZnTe/Si composite substrates mounted on indium free holders. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) based two-terminal devices, such as Schottky barrier diodes (SBDs), p-i-n diodes and light-emitting diodes (LEDs) are essential components for power conversion and optoelectronic applications, due to superior material properties including wide band gap (3.4 eV), high electron velocity, and large critical breakdown field. This article reviews the recent progress made in GaN two-terminal devices grown on lattice-mismatched Si substrates. Advances in material epitaxy, device design, and fabrication technology are illustrated for GaN diodes. A comprehensive overview of static and dynamic characteristics for both quasi- and fully-vertical p-i-n diodes are presented. With the developments of device design and processing technologies, various cracks-free LEDs-on-Si are achieved with wide spectrum coverage and improved efficiency. Nanowire LEDs and micro-LED display using GaN-on-Si epitaxy are also discussed. In addition, monolithic integration of GaN diodes with transistors as well as photodetectors enables creation of compact components with much reduced parasitic and small footprint, unlocking great potential of GaN-based device technology for versatile functionalities. [ABSTRACT FROM AUTHOR]

We have fabricated Ag/Al/sub 2/O/sub 3//Al tunnel junctions on Si substrates using a new process. This process was developed to fabricate superconducting tunnel junctions (STJs) on the surface of a superconductor. These junctions allow us to study the proximity effect of a superconducting Al film on a normal metal trapping layer. In addition, these devices allow us to measure the hot-electron diffusion constant using a single junction. Lastly these devices will help us optimize the design and fabrication of tunnel junctions on the surface of high-Z, ultra-pure superconducting crystals. [ABSTRACT FROM PUBLISHER]

Hall mobilities and resistance area products RoA of infrared diodes in epitaxial Pb1-xSnxSe layers on CaF2 covered Si(111) substrates were correlated with threading dislocation densities p. The low temperature saturation Hall mobilities were entirely determined by p and proportional to their mean spacing 1/ √ρ. For the photodiodes, the R0A values at low temperatures were inversely propor-tional to ρ. A model where each dislocation in the active area of the diodes causes a shunt resistance correctly describes the results, the value of this resistance for a single dislocation is 1.2 GΩ for PbSe at 85K. The dislocation densities were in the 2 × 107 to 5 × 108cm-2 range for the 3-4 μm thick as-grown layers. Higher R0A values are obtainable by lowering these densities by thermal annealing, which sweeps the threading ends of the misfit dislocations to the edges of the sample. [ABSTRACT FROM AUTHOR]

Orientation dependence of HgCdTe epilayers grown by MOCVD on Si substrates was studied. Substrate orientation is considered to be one of the most sensitive factors to enable hetero-epitaxial growth on silicon substrates, especially in the case of a low temperature growth process. The present work was carried out with characterized features of a low temperature process for HgCdTe growth on Si and using a thin CdTe buffer layer. The (100), (100) misoriented toward [110], (311), (211), (111), and (331) oriented Si substrates were used in the present work. The best results were obtained on (211)Si substrates with an x-ray full width at half maximum of 153 arc sec for a 5 (im thickness HgCdTe layer and 69 arc sec for a 10 um thickness layer. It was found that the effective lattice mismatch of CdTe/Si heterosystem was reduced to 0.6% (for the 611 lattice spacing of CdTe and 333 spacing of Si) in the case of (133)CdTe/(211)Si. [ABSTRACT FROM AUTHOR]

Ferroelectric BaTiO thin films were deposited on single crystal Si substrates by radio-frequency magnetron sputtering. Bilayer structures of BaTiO thin films, either amorphous on polycrystalline (A/P) or polycrystalline on microcrystalline (P/M), were utilized to reduce the leakage current and to enhance the dielectric constant of the films compared to single polycrystalline and amorphous layer structures, respectively. Relatively lower charge density, determined by the capacitance-voltage measurement on the capacitors with a configuration of Au/ BaTiO/p-Si/Al, was detected for the BaTiO thin film with a structure of P/M. The current-voltage characteristics of the Al/SiO(~1.8 nm)/p-Si/Al diodes fabricated on the Si after removing BaTiO layers gave direct evidence of the preservation of the Si surface crystal by using a P/M instead of a A/P structure. This was further confirmed by the Auger electron spectroscopy analysis on the samples. [ABSTRACT FROM AUTHOR]

Single domain CdTe(111)B has been grown on Si(001) substrates tilted 1 2, and 4 toward [110]. All the layers started with a double-domain structure, then a transition from a double- to a single-domain was observed by reflection high energy electron diffraction. A microscopic picture of this transition is presented. We also measured the tilt between CdTe(111)B and Si(001). The result does not follow the tilt predicted by the currently existing model. A new model of the microscopic mechanism of CdTe(111)B growth is presented. New evidence indicates that optimizing the tilt of the substrate surface is very crucial in improving the CdTe(111)B crystal quality. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline cubic indium oxide (In2O3) thin films were successfully grown without catalyst on the different orientation of Si substrates. In2O3 thin films have been synthesized by thermal evaporation of indium on unheated Si substrates, followed by wet oxidation process. The structural and optical properties of the In2O3 films were studied in terms of different substrates orientation. Through the Scherrer structural analysis revealed nanocrystalline structure for In2O3 films grown on Si (110), Si (100) and Si (111) orientations with crystallite size of 2.53, 3.36 and 3.43nm, respectively. Photoluminescence spectra showed a strong and broad emission at 570nm with two shoulders at 547nm and 604nm which related to oxygen vacancies. The band gap of polycrystalline In2O3 is determined as 2.15±0.15eV. [Copyright &y& Elsevier]