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As the scaling of integrated circuits based on silicon semiconductor becomes increasingly challenging due to the minimum feature size is close to the physical limit, the urgent demand for alternative strategies has fueled the rapid growth of technique and material innovations. Here, we report on the fabrication of vertically-stacked ambipolar complementary field-effect transistor (CFET) that is fully composed of two-dimensional materials of WSe2/h-BN/graphene/h-BN/WSe2 heterostructure. The ambipolar feature of the top and bottom WSe2 FET enables a switchable inverter behavior with a favorable voltage gain up to 75, which can work in both the first and third quadrant. Based on the switchable characteristic, a large voltage swing circuit for single photon avalanche detector (SPAD) is proposed without any bulky negative-voltage components. This work could open a new pathway for future 2D electronics and ultimate monolithic 3D high-density integration circuit.

Amorphous In–Ga–Zn–O (a-IGZO) thin-film transistor (TFT) memories with novel p-SnO/n-SnO2 heterojunction charge trapping stacks (CTSs) are investigated comparatively under a maximum fabrication temperature of 280 °C. Compared to a single p-SnO or n-SnO2 charge trapping layer (CTL), the heterojunction CTSs can achieve electrically programmable and erasable characteristics as well as good data retention. Of the two CTSs, the tunneling layer/p-SnO/n-SnO2/blocking layer architecture demonstrates much higher program efficiency, more robust data retention, and comparably superior erase characteristics. The resulting memory window is as large as 6.66 V after programming at 13 V/1 ms and erasing at –8 V/1 ms, and the ten-year memory window is extrapolated to be 4.41 V. This is attributed to shallow traps in p-SnO and deep traps in n-SnO2, and the formation of a built-in electric field in the heterojunction.

Recent advances in van der Waals heterostructures have extensively promoted the development of new-generation electronic devices. However, the normally utilized mechanical exfoliation method for preparing two-dimensional semiconductors is not scalable for circuit-level application. Herein, the fabrication and characterization of wafer-scale heterostructure arrays composed of multilayer 2H-MoTe2 and single-layer 2H-MoS2 are demonstrated. Owing to the type-II band alignment facilitating efficient electron–hole separation, the devices fabricated by the p-MoTe2/n-MoS2 heterostructure exhibit an excellent gate-tunable PN diode behavior, with a rectification ratio of over 103 and a self-powered photocurrent with a remarkable on–off ratio of ∼103 at a zero bias voltage. Complementary inverter arrays based on p-MoTe2/n-MoS2 are also demonstrated. The scalable production of p–n junction devices and complementary inverters paves the way for future integrated platforms in photoelectric detection and logic computation.

Flash memory with high operation speed and stable retention performance is in great demand to meet the requirements of big data. In addition, the realisation of ultrafast flash memory with novel functions offers a means of combining heterogeneous components into a homogeneous device without considering impedance matching. This report proposes a 20 ns programme flash memory with 108 self-rectifying ratios based on a 0.65 nm-thick MoS2-channel transistor. A high-quality van der Waals heterojunction with a sharp interface is formed between the Cr/Au metal floating layer and h-BN tunnelling layer. In addition, the large rectification ratio and low ideality factor (n = 1.13) facilitate the application of the MoS2-channel flash memory as a bit-line select transistor. Finally, owing to the ultralow MoS2/h-BN heterojunction capacitance (50 fF), the memory device exhibits superior performance as a high-frequency (up to 1 MHz) sine signal rectifier. These results pave the way toward the potential utilisation of multifunctional memory devices in ultrafast two-dimensional NAND-flash applications.

In this work, wafer-scale continuous and uniform MoS2/(HfO2) x (Al2O3)1−x (HfAlO) heterojunctions were prepared by atomic layer deposition. The energy band alignment of MoS2/HfAlO heterojunctions was systematically investigated using x-ray photoelectron spectroscopy. The valence band offsets were deduced to be 3.19 ± 0.1, 3.01 ± 0.1, 2.94 ± 0.1, and 2.91 ± 0.1 eV for the heterojunctions of MoS2/Al2O3, MoS2/(HfO2)0.45(Al2O3)0.55, MoS2/(HfO2)0.60(Al2O3)0.40 and MoS2/(HfO2)0.78(Al2O3)0.22, while the conduction band offsets were measured as 2.51 ± 0.1, 2.17 ± 0.1, 2.00 ± 0.1, and 1.85 ± 0.1 eV, respectively. All MoS2/HfAlO interfaces exhibited type-I band alignment. Furthermore, a MoS2 field-effect transistor with HfAlO as the gate dielectric layer was fabricated, and the gate leakage of the device was only a few picoamperes, which ensured high reliability and low power consumption. These encouraging results suggest that HfAlO is a promising dielectric material for applications in MoS2-based electronics and optoelectronics.

An asymmetric dual-gate (DG) MoS2 field-effect transistor (FET) with ultrahigh electrical performance and optical responsivity using atomic-layer-deposited HfO2 as a top-gate (TG) dielectric was fabricated and investigated. The effective DG modulation of the MoS2 FET exhibited an outstanding electrical performance with a high on/off current ratio of 6 × 108. Furthermore, a large threshold voltage modulation could be obtained from −20.5 to −39.3 V as a function of the TG voltage in a DG MoS2 phototransistor. Meanwhile, the optical properties were systematically explored under a series of gate biases and illuminated optical power under 550 nm laser illumination. An ultrahigh photoresponsivity of 2.04 × 105 AW−1 has been demonstrated with the structure of a DG MoS2 phototransistor because the electric field formed by the DG can separate photogenerated electrons and holes efficiently. Thus, the DG design for 2D materials with ultrahigh photoresponsivity provides a promising opportunity for the application of optoelectronic devices.

The electronic-photonic convergent systems can overcome the data transmission bottleneck for microchips by enabling processor and memory chips with high-bandwidth optical input/output. However, current silicon-based electronic-photonic systems require various functional devices/components to convert high-bandwidth optical signals into electrical ones, thus making further integrations of sophisticated systems rather difficult. Here, we demonstrate thin-film transistor-based photoelectric memories employing CsPbBr3/CsPbI3 blend perovskite quantum dots (PQDs) as a floating gate, and multilevel memory cells are achieved under programming and erasing modes, respectively, by imputing high-bandwidth optical signals. For different bandwidth light input (i.e. 500–550, 575–650 and 675–750 nm) with the same intensity, three levels of programming window (i.e. 3.7, 1.9 and 0.8 V) and erasing window (i.e. −1.9, −0.6 and −0.1 V) are obtained under electrical pulses, respectively. This is because the blend PQDs have two different bandgaps, and different amounts of photo-generated carriers can be produced for different wavelength optical inputs. It is noticed that the 675–750 nm light inputs have no effects on both programming and erasing windows because of no photo-carriers generation. Four memory states are demonstrated, showing enough large gaps (1.12–5.61 V) between each other, good data retention and programming/erasing endurance. By inputting different optical signals, different memory states can be switched easily. Therefore, this work directly demonstrates high-bandwidth light inputting multilevel memory cells for novel electronic-photonic systems.

Semiconductive two dimensional (2D) materials have attracted significant research attention due to their rich band structures and promising potential for next-generation electrical devices. In this work, we investigate the MoS2 field-effect transistors (FETs) with a dual-gated (DG) architecture, which consists of symmetrical thickness for back gate (BG) and top gate (TG) dielectric. The thickness-dependent charge transport in our DG-MoS2 device is revealed by a four-terminal electrical measurement which excludes the contact influence, and the TCAD simulation is also applied to explain the experimental data. Our results indicate that the impact of quantum confinement effect plays an important role in the charge transport in the MoS2 channel, as it confines charge carriers in the center of the channel, which reduces the scattering and boosts the mobility compared to the single gating case. Furthermore, temperature-dependent transfer curves reveal that multi-layer MoS2 DG-FET is in the phonon-limited transport regime, while single layer MoS2 shows typical Coulomb impurity limited regime.

The effects of x-ray irradiation on the mechanically exfoliated quasi-two-dimensional (quasi-2D) β-Ga2O3 nanoflake field-effect transistors (FETs) under the condition of biasing voltage were systematically investigated for the first time. It has been revealed that the device experienced two stages during irradiation. At low ionizing doses ( 240 krad), the device characteristics are dominated by the radiation-induced structural or compositional deterioration. The newly-generated e-traps are found located at the SiO2/β-Ga2O3 interface. This study shed light on the future radiation-tolerant device fabrication process development, paving a way towards the feasibility and practicability of β-Ga2O3-based devices in extreme-environment applications.

The coming information era has brought about a data explosion which requires smaller and smarter memory devices. In this paper, a ReS2 based high-k dielectric stack (Al2O3/ZrO2/Al2O3) memory was fabricated as a potential candidate for future storage and computing. The device exhibits preeminent electrical characteristics, such as high On/Off current ratio (over 106 ), large memory window (4 V at a 5 V sweep voltage), fast programming and erasing speed plus excellent retention ability. Besides, our devices beautifully emulated the short/long-term potentiation/depression behavior, which shows the good synaptic properties of our device. These excellent storage and synaptic properties are promising for a wide range of applications for our memory device in the future.

The active pixel image sensor based on a semi-floating gate transistor (SFGT-APS) has been proposed and investigated; however, the quantum efficiency (QE) and the sensitivity are too poor to meet low illumination intensity and high-speed application due to the shallow junction of photodiodes. In this work, we demonstrate a new structure, called buried photodiode semi-floating gate transistor active pixel image sensor (BSFGT-APS), which possesses enhanced QE, high sensitivity, and fast response speed. Moreover, BSFGT-APS has the same fill factor with SFGT-APS, which is 55% with a 1 μm2 photodiode in 0.13 μm process. The basic device characteristics were investigated by Sentaurus TCAD simulation, including potential of photodiode, transient response, dark current, conversion gain, and full well capacity.

Chemical vapor deposition synthesis of semiconducting transition metal dichalcogenides (TMDs) offers a new route to build next-generation semiconductor devices. But realization of continuous and uniform multilayer (ML) TMD films is still limited by their specific growth kinetics, such as the competition between surface and interfacial energy. In this work, a layer-by-layer vacuum stacking transfer method is applied to obtain uniform and non-destructive ML-MoS2 films. Back-gated field effect transistor (FET) arrays of 1L- and 2L-MoS2 are fabricated on the same wafer, and their electrical performances are compared. We observe a significant increase of field-effect mobility for 2L-MoS2 FETs, up to 32.5 cm2 V-1 s-1, which is seven times higher than that of 1L-MoS2 (4.5 cm2 V-1 s-1). Then we also fabricated 1L-, 2L-, 3L-, and 4L-MoS2 FETs to further investigate the thickness-dependent characteristics of transferred ML-MoS2. Measurement results show a higher mobility but a smaller current on/off ratio as the layer number increases, suggesting that a balance between mobility and current on/off ratio can be achieved in 2L- and 3L-MoS2 FETs. Dual-gated structure is also investigated to demonstrate an improved electrostatic control of the ML-MoS2 channel.

The excellent performance of electronic and optoelectronic devices based on two-dimensional materials, including graphene and transition metal dichalcogenides (TMDs) such as MoS2 and WSe2, has inspired enthusiastic research on their potential applications in many fields. Numerous studies have been done on van der Waals heterojunctions, but a full understanding of the relationship between the contact barrier and the rectification ratio in these structures is still uncertain. In this work, we investigate the electrical properties of a lateral P–N junction based on an MoS2 and WSe2 heterojunction and extract the Schottky barrier heights in the contact areas. The barrier heights extracted from the device for MoS2-metal, WSe2-metal and P–N junction, are 71.6 meV, 232.7 meV, and 30.9 meV respectively. The result indicates that the rectification ratio of a lateral P–N junction mainly comes from the Schottky barrier between WSe2 and metal, which is distinct from traditional P–N junctions based on silicon. Our work quantitatively analyzes the effect of the contact barrier and the P–N junction on the electrical characteristics of the rectification ratio, which provides a deep understanding of the electronic transport characteristics of P–N heterojunctions and paves the way for the construction of novel electronic devices based on van der Waals heterojunctions in the future.

The energy band offsets between indium–gallium–zinc oxide (IGZO) and β-Ga2O3 were examined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The Ga 2p spectra from the heterojunction contributed by the upper IGZO film and the β-Ga2O3 substrate were deconvoluted into two sub-peaks with the binding energy difference of 0.3 eV, in good agreement with the theoretical model. Meanwhile, the bandgaps of IGZO and β-Ga2O3 were measured to be 3.44 ± 0.1 and 4.64 ± 0.1 eV from the ultraviolet–visible (UV–vis) transmittance spectra. The valence and conduction band offsets between the IGZO and β-Ga2O3 were consequently determined to be 0.49 ± 0.05 and 0.71 ± 0.1 eV, respectively. These findings reveal that IGZO is an attractive intermediate semiconductor layer (ISL) for reducing the electron barrier height at metal/Ga2O3 interfaces.

Metal–insulator–metal (MIM) capacitors with atomic-layer-deposited Al2O3–HfO2 laminated and sandwiched dielectrics have been fabricated and electrically compared for analog circuit applications. The experimental results indicate that the laminated dielectrics exhibit much better leakage and breakdown characteristics than the sandwiched ones while maintaining higher capacitance densities and acceptable voltage linearity. In respect of the 1 nm Al2O3 and 10 nm HfO2 laminated dielectric, the resulting capacitor offers an extremely low leakage current of 2.4 × 10−9 A cm−2 at 8 V and a breakdown electric field of ~3.3 MV cm−1 at 125 °C together with a capacitance density of ~3.1 fF µm−2 and voltage coefficients of capacitance of 100 ppm V−2 and −80 ppm V−1 at 100 kHz. The superiority of the laminated dielectrics correlates with inhibition of HfO2 crystallization, discontinuity of the grain boundary channels from the top to the bottom and changes of the dielectric electronic properties due to the bonding and polarization effects at the multi-interfaces.

Cluster calculations employing hybrid density functional theory have been carried out to examine the initial surface reactions in atomic layer deposition (ALD) of TiN thin films on the SiO(2) surface using TiCl(4) and NH(3) as precursors. The potential energy surface (PES) of both half-reactions at different temperatures is presented. The first half-reaction between TiCl(4) with the SiO(2) surface is activated with an activation barrier of 0.78 eV and an exothermicity of 0.38 eV, suggesting that it is thermodynamically favourable. Also, the NH(3) half-reaction begins with the formation of amido complexes by the replacement of Cl atoms by NH(2), which is endothermic by 0.58 eV with a physisorbed HCl state (HCl-PS1). Formation of the amido complexes can be followed by an elimination reaction to form imido complexes, which has a relatively high activation barrier of 2.51 eV. In addition, the effect of the reaction temperature on the Cl impurity concentrations and film growth rate in the ALD process is also discussed.

Hybrid density functional theory has been used to investigate the initial surface reaction mechanism in atomic layer deposition (ALD) of Al2O3 on the hydroxylated GaAs(001)-4 x 2 surface. The precursors for ALD of Al2O3' are trimethylaluminium (TMA) and H2O as the aluminium and oxygen sources. For the first half-reaction between TMA with the GaAs surface the calculated activation barrier is 15.4 kcal mol(-1), and the H2O half-reaction proceeds by a mechanism similar to that of the first half-reaction, resulting in an activation barrier of 27.6 kcal mol(-1). Both half-reactions are thermodynamically favourable, exothermic by 52.0 and 43.6 kcal mol(-1) relative to the reactants, respectively.

Ultrathin layered two-dimensional (2D) semiconductors like MoS2 and WSe2 have received a lot of attention because of their excellent electrical properties and potential applications in electronic devices. We demonstrate a charge-trap memory with two different tunable operation modes based on a few-layer MoS2 channel and an Al2O3/HfO2/Al2O3 charge storage stack. Our device shows excellent memory properties under the traditional three-terminal operation mode. More importantly, unlike conventional charge-trap devices, this device can also realize the memory performance with just two terminals (drain and source) because of the unique atomic crystal electrical characteristics. Under the two-terminal operation mode, the erase/program current ratio can reach up to 104 with a stable retention property. Our study indicates that the conventional charge-trap memory cell can also realize the memory performance without the gate terminal based on novel two dimensional materials, which is meaningful for low power consumption and high integration density applications.

When integrating MoS2 flakes into scaling-down transistors, the short-channel effect, which is severe in silicon technology below 5-nanometer, can be avoided effectively. MoS2 transistors not only exhibit a high on/off ratio but also demonstrate a rapid switching speed. According to the theoretical calculation, the thermionic limit subthreshold slope (SS) of the ideal device could reach 60 mV/dec. However, due to the confinement of defects from substrates or contamination during the process, the SS deteriorates to more than 300 mV/dec, causing serious power consumption. In this work, we optimize the SS through structure design of MoS2 transistors. The suspended transistors exhibit a high on/off ratio of 107 and a minimum SS of 63 mV/dec with an ultralow standby power at room temperature. This study demonstrates the promising potential of structure design for electronic devices with ultralow-power switching behaviors.

Wafer-level integration of 2D transition metal disulfide is the key factor for future large-scale integration of the continuously scaling-down devices, and has attracted great attention in recent years. Compared with other ultra-thin film growth methods, atomic layer deposition (ALD) has the advantages of excellent step coverage, uniformity and thickness controllability. In this work, we synthesized large-scale and thickness-controllable MoS2 films on sapphire substrate by ALD at 150 °C with molybdenum hexcarbonyl and hexamethyldisilathiane (HMDST) as precursors followed by high-temperature annealing in sulfur atmosphere. HMDST is introduced for the first time to enable a toxic-free process without hazardous sulfur precursors such as H2S and CH3SSCH3. The synthesized MoS2 retains the inherent benefits from the ALD process, including thickness controllability, reproducibility, wafer-level thickness uniformity, and high conformity. Finally, field-effect transistor (FET) arrays were fabricated based on the large-area ALD MoS2 films. The top-gate FETs exhibited excellent electrical performance such as high on/off current ratio over 103 and peak room-temperature mobility up to 11.56 cm2 V−1 s−1. This work opens up an attractive approach to realize the application of high-quality 2D materials with wafer scale homogeneity.

Heterostructure field-effect transistors (hetero-FETs) are experimentally demonstrated, consisting of van der Waals heterostructure channels based on a 2D semiconductor. By optimally selecting the band alignment of the heterostructure channels, different output characteristics of the hetero-FETs were achieved. In atomically thin WSe2/MoS2 hetero-FET with staggered energy band, the oscillating transfer characteristic and negative transconductance were realized. With near-broken-gap alignment in the MoTe2/SnSe2 heterostructure channel, a superior reverse-biased current was obtained in the hetero-FETs, which can be analyzed as typical tunneling current. Our study on the hetero-FET-based atomically thin van der Waals heterostructure channel, provides significant inspiration and reference to novel heterostructure FETs.

As technology node shrinks, aggressive design rules for contact and other back end of line (BEOL) layers continue to drive the need for more effective full chip patterning optimization. Resist top loss is one of the major challenges for 28 nm and below technology nodes, which can lead to post-etch hotspots that are difficult to predict and eventually degrade the process window significantly. To tackle this problem, we used an advanced programmable illuminator (FlexRay) and Tachyon SMO (Source Mask Optimization) platform to make resist-aware source optimization possible, and it is proved to greatly improve the imaging contrast, enhance focus and exposure latitude, and minimize resist top loss thus improving the yield.

We investigated the resistive switching characteristics of a SiCOH low-k-material-based resistive random access memory (RRAM) in this study. This SiCOH-based RRAM is fully compatible with backend CMOS technology, which is extremely important for its applicability. The device demonstrated here had higher performance characteristics than a conventional SiO2-based RRAM, such as a higher ON/OFF ratio (around 102), and a higher cycling endurance in an ambient environment. Taken together, these characteristics make the device a promising candidate for next-generation nonvolatile applications.

Two-dimensional layered materials (2DLMs) are radically different from conventional bulk semiconductors, and major challenges in achieving practical 2DLM devices with good performance lie in the areas of improving the electrical contacts that connect 2DLMS with electrodes rather than in improving the quality of the channel material itself. To meet this challenge, we have devised a promising large-scale synthesis method for few-layer MoS2 film integrated with unique fabrication process that provides good contact. A thin layer of Mo was first deposited using sputtering evaporation and defined by a shadow mask, instead of immediate sulfurization in a chemical vapor deposition (CVD) furnace. Au contact electrodes were then deposited on Mo, followed by further sulfurization, which readily provides source-drain electrodes for synthesized MoS2. Top-gated transistors based on such MoS2 film show improved device performance compared to transistors fabricated using the traditional method. The transfer line method was further applied to verify that the proposed method could effectively decrease the contact resistance by more than 10 times, which can be attributed to the incomplete sulfurization of Mo atoms beneath the Au electrodes. It is envisioned that the proposed method could eventually be used to provide uniform and low contact resistance for CVD-grown 2DLM devices.

Van der Waals heterostructures, composed of individual two-dimensional material have been developing extremely fast. Synthesis of van der Waals heterostructures without the constraint of lattice matching and processing compatibility provides an ideal platform for fundamental research and new device exploitation. We review the approach of synthesis of van der Waals heterostructures, discuss the property of heterostructures and thoroughly illustrate the functional van der Waals heterostructures used in novel electronic and photoelectronic device.

The interactions between magnetron-sputtered Cu and plasma-enhanced chemical-vapour-deposited a-SiCOF film have been investigated via x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). High-resolution C 1s, Cu 2p, O 1s, Si 2p and F 1s XPS spectra for the samples before and after annealing are collected. The results show that the C-Cu bond is not observed at the interface of Cu/a-SiCOF before or after the annealing. Moreover, the annealing causes the obvious shifts of Cu 2p3/2, C 1s, O 1s and Si 2p photoelectron peaks toward higher binding energy, and the underlying reasons are discussed in detail. The AES spectra of Cu L3M4,5M4,5 with the etching time reveal that some chemical reactions take place at the interface during the sputtering deposition of copper on the a-SiCOF film, and possible reaction mechanisms are also presented. The Cu 2p3/2 XPS spectra and the SEM graphs demonstrate that the annealing enhances the interdiffusion between Cu and a-SiCOF film.

The preparation of a-SiOCF films from Si(OC2H5)4, C4F8 and/or Ar using a plasma-enhanced chemical vapour deposition method is reported. The chemical bonding structures of the films are analysed by high-resolution x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The results show that the films contain F-Si-O-Si, Si-OH, Si-O-Si, C-CF and C-F configurations. However, as for the film deposited from the feeding gases with Ar, a C-C configuration is also included in addition to the above-mentioned configurations. This indicates that the existence of Ar in the plasma leads to the formation of a fluorocarbon structure with a high degree of cross-linking. No evidence reveals the presence of a Si-C bond in the film, so it is believed that the fluorocarbon is perhaps embedded into the matrix of SiOF.

Two-dimensional layered materials (2DLMs) have attracted broad interest from fundamental sciences to industrial applications. Their applications in memory devices have been demonstrated, yet much still remains to explore optimal materials and device structure for practical application. In this work, a forming-free, bipolar resistive switching behavior are demonstrated in 2D TiO2-based resistive random access memory (RRAM). Physical adsorption method is adopted to achieve high quality, continuous 2D TiO2 network efficiently. The 2D TiO2 RRAM devices exhibit superior properties such as fast switching capability (20 ns of erase operation) and extremely low erase energy consumption (0.16 fJ). Furthermore, the resistive switching mechanism is attributed to the formation and rupture of oxygen vacancies-based percolation path in 2D TiO2 crystals. Our results pave the way for the implementation of high performance 2DLMs-based RRAM in the next generation non-volatile memory (NVM) application.

Control of the work function of molybdenum disulfide (MoS2) under ultrathin metal was investigated using in situ metal deposition and direct ultraviolet photoelectron spectroscopy measurement in an ultra-high vacuum system. When the metal thickness turned from two dimensional into bulk, the work function was also raised up at the nickel-MoS2 interface, barely changed at the titanium-MoS2 interface and lowered at the hafnium-MoS2 interface. Meanwhile, the mechanisms of charge transfer and band alignment with metal deposition were also discussed. The Schottky barrier at metal-MoS2 interfaces could be tailored by both types and thicknesses of deposited metal. The low work function metal was a good indicator for MoS2 contact electrodes. It paved the way towards future high performance MoS2 device applications.

Two-dimensional atomic-layered material is a recent research focus, and single layer Ta2O5 used as gate dielectric in field-effect transistors is obtained via assemblies of Ta2O5 nanosheets. However, the electrical performance is seriously affected by electronic defects existing in Ta2O5. Therefore, spectroscopic ellipsometry is used to calculate the transition energies and corresponding probabilities for two different charged oxygen vacancies, whose existence is revealed by x-ray photoelectron spectroscopy analysis. Spectroscopic ellipsometry fitting also calculates the thickness of single layer Ta2O5, exhibiting good agreement with atomic force microscopy measurement. Nondestructive and noncontact spectroscopic ellipsometry is appropriate for detecting the electrical defects level of single layer Ta2O5.

Surface-plasmon mediated photoluminescence emission enhancement has been investigated for ZnO nanowire (NW)/Pt nanoparticle (NP) nanostructures by inserting an Al2O3 spacer layer. The thickness of the Al2O3 spacer layer and of the Pt NPs capped on the ZnO NWs are well controlled by atomic layer deposition. It is found that the photoluminescence property of the ZnO NW/Al2O3/Pt hybrid structure is highly tunable with respect to the thickness of the inserted Al2O3 spacer layer. The highest enhancement (∼14 times) of the near band emission of ZnO NWs is obtained with an optimized Al2O3 spacer layer thickness of 10 nm leading to a ultraviolet-visible emission ratio of 271.2 compared to 18.8 for bare ZnO NWs. The enhancement of emission is influenced by a Forster-type non-radiative energy transfer process of the exciton energy from ZnO NWs to Pt NPs as well as the coupling effect between excitons of ZnO NWs and surface plasmons of Pt NPs. The highly versatile and tunable photoluminescence properties of Pt-coated ZnO NWs achieved by introducing an Al2O3 spacer layer demonstrate their potential application in highly efficient optoelectronic devices.

A laterally diffused metal-oxide-semiconductor (LDMOS) device design with an enhanced p-well and double p-epitaxial structure is investigated for device ruggedness improvement while keeping its high device performance under high frequency. Based upon the device design, radio-frequency (RF) LDMOS transistors for GSM (global system for mobile communication) application have been fabricated by using 0.35 μm CMOS technologies. Experimental data show that the proposed device achieves a breakdown voltage of 70 V, output power of 180 W. The RF linear gain is over 20 dB and the power added efficiency (PAE) is over 70% with the frequency of 920 MHz. In particular, it can pass the 20 : 1 voltage standing wave ratio (VSWR) load mismatch biased at drain DC supply voltage of 32 V and output power at 10-dB gain compression point (P10dB). The device ruggedness has been remarkably improved by using the proposed device structure.

In this paper the annealing effects in N2 on the electrical characteristics of a TiN/HfO2/GeON/p-Ge capacitor are investigated. Well behaved capacitance–voltage curves were obtained for the sample annealed at 400 °C for 3 min in N2. A negligible hysteresis was demonstrated comparing with a hysteresis of 0.5 V for the as-deposited sample. The suppression of hysteresis is attributed to the reduction of electron traps in the dielectric layer, which is verified by the MOS pulse method. Besides, the interface states' density is also greatly reduced by annealing in N2 and confirmed by the conductance method.

In this work, first-principles calculation based on the density functional theory was applied to study Cu adhesion on the surfaces of Rh(111), Ir(111), Pd(111), Ta(110), Mo(110), Co(0001), Os(0001), and Ru(0001), on which the adsorption energy, electron density difference, and geometrical structures of Cu were investigated. The analysis of the calculated and experimental results shows that the atomic chemical interaction, surface lattice mismatch, and crystal lattice type have marked effects on Cu adhesion on glue layers. Cu atoms on all the metal surfaces studied in this work are more likely to form the fcc structure with a quasi-(111) orientation. The coupling effect of the large surface lattice mismatch and the lattice type difference between Cu and the metal surface can greatly reduce Cu adhesion ability. Among all the studied metals, Ir and Os showed comparable adhesion ability to Ru and can be considered as promising Cu glue layers for Cu interconnects.

High-constant dielectrics have gained considerable attention due to their wide applications in advanced devices, such as gate oxides in metal–oxide–semiconductor devices and insulators in high-density metal–insulator–metal capacitors. However, the theoretical investigations of these materials cannot fulfil the requirement of experimental development, especially the requirement for the accurate description of band structures. We performed first-principles calculations based on the hybrid density functionals theory to investigate several typical high-k dielectrics such as Al2O3, HfO2, ZrSiO4, HfSiO4, La2O3 and ZrO2. The band structures of these materials are well described within the framework of hybrid density functionals theory. The band gaps of Al2O3, HfO2, ZrSiO4, HfSiO4, La2O3 and ZrO2are calculated to be 8.0 eV, 5.6 eV, 6.2 eV, 7.1 eV, 5.3 eV and 5.0 eV, respectively, which are very close to the experimental values and far more accurate than those obtained by the traditional generalized gradient approximation method.

Structured ZnO films have been fabricated on soda-lime glass slides at a low temperature (80–85 °C) by a chemical bath deposition method in one step without seed layers. Mixed aqueous solutions of zinc sulfate, ammonia and thiourea were used at alkaline conditions. The influence of the ammonia concentration in the initial solution on the property of the deposited film was investigated systematically. The morphology, structural and optical properties of the deposited films were examined and characterized by x-ray diffraction (XRD), energy-dispersive spectroscopy x-ray diffraction (EDX), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy. Structural analyses with XRD, EDX and SEM revealed that the formed films exhibit a wurtzite hexagonal phase. The deposited film was more preferentially oriented in the (0 0 2) direction with an increase in the ammonia concentration from 0.75 to 2 mol l−1. The optical-phonon E2 mode at 437 cm−1 in the Raman spectrum, together with the XRD and EDX analyses, showed that flower-like and columnar crystalline ZnO films were formed in two ammonia concentration ranges, 0.75–1.4 mol l−1 and 1.6–2.0 mol l−1, respectively. Furthermore, PL spectra showed strong and high intensity peaks of UV emission with suppressed green emission for these deposited ZnO films. ZnS films were formed with a high ammonia concentration of 3.0 M. The formation mechanisms of ZnO, Zn(OH)2 and ZnS phases were discussed.

Growth of uniformly distributed Ru nanocrystals on Al2O3 is demonstrated via atomic layer deposition using bis(cyclopentadienyl)-ruthenium and oxygen precursors. X-ray photoelectron spectroscopy analyses reveal that metallic Ru nanocrystals were formed in this experiment, and the RuO2 surface is due to oxidation of Ru when exposed to air. The metal-oxide-silicon capacitors with Ru nanocrystals embedded into Al2O3 are electrically measured, exhibiting obvious memory effects such as a large hysteresis memory window of 3.4 V for the sweeping gate voltage of −2.5/ + 8 V and a significant flat-band voltage shift of 3.2 V under the programming of 10 V/1 ms, i.e. an effective electron injection rate as fast as 1.78 × 10−6 C cm−2 ms−1. This relates to the program mechanism of direct tunnelling and a large potential well depth.