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In this paper, the properties of indium nitride (InN) semiconductor films deposited by magnetron sputtering were studied. The effects of different substrates (Al 2 O 3 , ITO and Si) and different nitrogen-argon flow ratios on the crystal quality of InN films were compared. The crystal structure, surface morphology, optical and electrical properties of InN films were systematically studied. The results showed that the crystallization quality of InN thin film was the best when the flow ratio of nitrogen to argon was 30/0 on Al 2 O 3 substrate. Then the p-NiO/n-InN/AlN heterojunction device was prepared on Al 2 O 3 by using AlN as buffer layer, and the electrical properties of the devices at different operating temperatures were analyzed. Finally, high rectification characteristics and good temperature stability were obtained. This study provides a reference for the preparation of InN films on different substrates and the application of InN-based devices. • The effects of different substrate types on the physical properties of InN films were studied. • The InN films with relatively good quality was obtained by magnetron sputtering. • Device with high rectification characteristics typical based on p-NiO/n-InN structure was prepared. • The influence of the operating temperature of the device on the rectification characteristics was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of substrate temperature and nitrogen to argon ratio on the physical properties of AlN films were studied. • An Au/i-AlN/n-GaN LED was fabricated, and a hole generation model and carrier transport and recombination mechanism were proposed. • The electroluminescence characteristics of Au/i-AlN/n-GaN LED at different temperatures were investigated. Aluminum nitride (AlN) film has a wide range of applications optoelectronic devices. In this paper, AlN thin films were prepared by magnetron sputtering method, the influence of substrate temperature and nitrogen-argon ratio on the structure, morphology and optical properties of AlN films were evaluated by X-ray diffractometer, scanning electron microscope and ultraviolet–visible spectrophotometer. The analysis showed that the AlN film exhibited better crystallization quality under the substrate temperature of 350 °C with a nitrogen-argon ratio of 5:40. In addition, an Au/i-AlN/n-GaN metal–insulator-semiconductor (MIS) structure device was fabricated based on high-quality AlN films. The current–voltage and electroluminescence characteristics of the device under different temperatures were studied in detail. The results showed that the device exhibited excellent rectification behavior at all operating temperatures, producing an intense UV emission (∼372 nm). This paper proposes a hole generation model and a carrier transport and recombination mechanism. The research results provide a new reference for the practical application of AlN films. [ABSTRACT FROM AUTHOR]

The aluminum nitride (AlN) films were deposited on Al 2 O 3 substrates at different nitrogen flow rates by radio frequency (RF) magnetron sputtering. The X-ray Diffraction (XRD) patterns indicated that the obtained AlN film exhibited significant (110) and (100) diffraction when the nitrogen flow rate was 4 sccm. The analysis of surface morphology by scanning electron microscope (SEM) showed that the surface morphology of AlN films had a transition from nanoparticles to long nanorods as the nitrogen flow rate was increased. Moreover, the optical transmittance of AlN films was decreased with the increase of nitrogen flow rates and the band gap energy varied from 4.48 to 5.58 eV. Afterwards, the prepared AlN film was used as a buffer layer to insert in the p-NiO/n-InN device, and the improvements of the buffer layer on transport behaviors of the device were studied. Furthermore, the device was placed in 30–110 °C to analyze the effect of temperature on the carrier transport mechanism. Finally, the long-term stability of the unpackaged device was also investigated, and the reasons for the deterioration of the device characteristics were analyzed. • The optimization of N 2 flow rates was important to develop high quality AlN films. • The effect of AlN buffer layer on I–V characteristics of the device was studied. • The logI-logV plots of device could be divided three regions on different voltages. • I–V characteristics of the device were studied in the temperature range of 30–110 °C. • Long term stability of the unpackaged diode was also investigated. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu 2 O), a far-reaching photon-absorption layer, is active in the field of solar cells and sensors. In this work, the Cu 2 O films prepared at low temperature by radio frequency (RF) magnetron sputtering holds a branch-like crystalline morphology, low optical transmittance and unsatisfactory carrier mobility. However, peroxidation will occur when thermal is excessive. By optimizing, the (111)-oriented monocrystal Cu 2 O films with trapping light structure are obtained through the rapid thermal annealing (RTA) process in N 2 atmosphere, and the carrier mobility is escalated by five times to 11.75 cm2/v·s. On this basis, we construct an Au/p-Cu 2 O/n-Si/Al device and keep the leakage current standing at 1.81 × 10−9 A and the rectification ratio (I F /I R) reaching 177. Surprisingly, the unpackaged device still maintains a rectification ratio of 44 and a considerable leakage current even operating at 120 °C. Finally, we have measured the photovoltaic characteristic and provided some optimization strategies for power conversion efficiency. • Have studied the thermal dependence of Cu 2 O photon-absorbing layer during sputtering process. • The (111)-oriented Cu 2 O films are obtained through the RTA process, and the carrier mobility is escalated by 5 times. • A p-Cu 2 O/n-Si heterojunction was constructed, which take an excellent rectifying characteristic and thermal stability. • The photovoltaic characteristic on Au/p-Cu 2 O/n-Si/Al device is observed and discussed. [ABSTRACT FROM AUTHOR]

Abstract: The surface acoustic wave (SAW) ultraviolet (UV) detector based on zinc oxide (ZnO) nanowire sensing layer was developed and fabricated in this paper. To improve the SAW device''s response characteristics, inter-digital transducers (IDTs) apodized by Morlet wavelet function and multiple couplers (MSC) were applied. ZnO nanowire materials were synthesized by Zinc thermal evaporation method. The ZnO nanowire sensing layer was coated onto the propagating area of the SAW devices, namely the sensing area, by transfer method as well as the multi-crystal ZnO sensing layer was deposited onto another device by magnetron sputtering for comparison. It was found that ZnO nanowire layer itself shows enhanced UV photoelectric response characteristics compared to sputtered ZnO film layer, which is acquired by characterizing their optical and photoelectrical properties. Under illumination of a UV light source, central frequency shifts of the two UV detectors were measured. An average central frequency shift of over 65kHz of the UV detector based on ZnO nanowire layer was observed under 150μW/cm2 365nm illumination for several on–off cycles while the one of the other detector was only about 8kHz. Moreover, the results indicate that the ZnO nanowire layer based SAW UV detector has good stability and repeatability. This kind of SAW UV detector with high sensitivity presents the potential for practical UV detection applications. [Copyright &y& Elsevier]

CuO films are expected to be an attractive photovoltaic material in the field of optoelectronic device. However, the applications of these films have been limited due to the difficulty in controlling the crystalline quality and conductivity as a result of the undesirable sensitivity to growth conditions. Herein, we report the preparation of CuO films by the radio frequency (RF) magnetron sputtering and then the as-grown films were annealed by the thermal annealing furnace under the annealing temperatures of 300, 500, 700 and 900 °C, respectively. The crystal structures, surface morphology, optical and electrical properties of CuO films were systematically investigated. The X-ray diffraction results revealed that the intensity of CuO (002) diffraction was significantly enhanced while the crystalline orientation was unchanged after annealing. Moreover, the crystal size, interplanar spacing and inhomogeneous strain were also determined. From the image of scanning electron microscope, the surface morphology of CuO films exhibited a transition from pyramid to oval shape with the increase of annealing temperature. The absorption measurement showed the band gap of prepared CuO films varied from 1.485 to 1.631 eV. Moreover, Hall effect indicated the mobility and carrier concentration of the CuO films could be adjusted from 0.026 to 0.316 cm2/v·s and 4.15 × 1018 to 9.23 × 1019 cm-3, respectively. • CuO films prepared by magnetron sputtering were annealed at different temperatures. • The crystal size, interplanar spacing and inhomogeneous strain were determined. • The crystal orientation was determined by texture coefficient and standard deviation. • The surface morphology exhibited a transition from pyramid to oval shape. • Annealing treatment could improve the crystallization quality of CuO films. [ABSTRACT FROM AUTHOR]

In x Al 1-x N alloys were prepared on Al 2 O 3 substrates using radio frequency magnetron sputtering. The physical properties of In x Al 1-x N alloys sputtered at different substrate temperatures were systematically studied. The results indicated that the sputtered In x Al 1-x N alloys had c-axis preferred orientation and exhibited phase separation under the substrate temperature over 450 °C. The In content was calculated about 0.62 according to the Vegard's law. It was found that the surface morphology of In 0.62 Al 0.38 N alloys showed a transition from nanodots to nanoclusters and disordered morphology as the substrate temperature was increased from 150 to 450 °C. This research will lay a good foundation for the application of In x Al 1-x N-based optoelectronic devices. • In x Al 1-x N alloys were sputtered by magnetron sputtering at different substrate temperature. • The substrate temperature is critical to effect the physical characteristics of In x Al 1-x N alloys. • The In metal could form good ohmic contact on InAlN alloy surface. • The band gap bending factor b was calculated to be 3.0 eV. [ABSTRACT FROM AUTHOR]

Silver oxide (Ag x O) has huge potential in the catalysts and semiconductor devices applications and thus it is of great significance to characterize its semiconductor properties. Here, by using the RF reactive magnetron sputtering method under different substrate temperatures, 40, 100, and 200 °C, respectively, three Ag x O films were prepared and their semiconductor properties were carefully investigated through X-ray diffraction, Hall measurement, transmittance and photoluminescence spectrum. The main phase of the Ag x O films sputtered at 40 and 100 °C is found to be AgO, while that sputtered at 200 °C is Ag 2 O. The resistivity of the Ag x O films increases with the substrate temperature and the mobility of the AgO films are about 21 and 15 cm 2 /V·s for the 40 and 100 °C deposited films, respectively. Photoluminescence measurement results suggest that the band gaps of Ag 2 O and AgO films are both 3.4 eV, and the emission bands in the visual light region indicate the existence of amount of defects in the Ag x O films. Moreover, the defect levels in the band gap deduced from the transmittance spectra are consistent with that from the photoluminescence spectra analysis. Besides, a metal-metal-semiconductor-metal structured X-ray detector was fabricated using the high-resistivity Ag 2 O film to explore its photoconductive response to the X-ray. The signal to noise ratio is 65 and the sensitivity is 4.2 nC/Gy at 5 V bias voltage using the 30 kV X-ray source with the dose rate of 1.53 Gy/s. [ABSTRACT FROM AUTHOR]

CuO had huge application prospects in the fields of semiconductor optoelectronic devices. However, the preparation of high-quality CuO films was still an urgent problem to be solved. Herein, we prepared CuO films at different sputtering pressures (0.6–2.1 Pa) by magnetron sputtering technology. The experiment results showed that the sputtering pressure had an obvious effect on the optical properties, structure, morphology and electrical properties of CuO films. It showed that relatively better CuO films could be prepared at 1.6 Pa. Moreover, Hall effect indicated that the change of ambient temperature had an obvious effect on the resistivity and carrier concentration of CuO films. Correspondingly, the p-CuO/n-GaN heterojunction device was fabricated, and the relationship between carrier transport characteristics and ambient temperature was studied. Ambient temperature had obvious influence on the turn-on voltage and rectification ratio of the device. This work provided a basis for the practical application of CuO-based optoelectronic devices. • The effect of sputtering pressure on the physical properties of CuO film was studied. • The effect of ambient temperature on the electrical properties of CuO films was studied. • Device with high rectification ratio based on p-CuO/n-GaN structure was prepared. • The influence of operating temperature on the carrier transport properties was studied. [ABSTRACT FROM AUTHOR]

In recent years, GaN materials have been applied to the field of optoelectronic devices due to their excellent photoelectric properties, especially in the field of light-emitting diodes, which has attracted considerable attention. In this article, we use structural engineering methods to further improve the performance of GaN-based ultraviolet light-emitting diodes. The magnetron sputtering and annealing treatment were used to prepare ultraviolet light-emitting diodes based on p-NiO/i-Ga 2 O 3 /n-GaN and p-NiO/n-GaN heterojunction structure. X-ray diffractometer, field emission scanning electron microscope and ultraviolet-visible spectrophotometer were used to study the crystal quality, surface morphology, and optical properties of Ga 2 O 3 film. Compared with the p-NiO/n-GaN heterojunction diode, the p-NiO/i-Ga 2 O 3 /n-GaN heterojunction diode exhibits better rectification characteristics and more excellent electroluminescence characteristics. Under the injection voltage of 35 V, the EL spectrum intensity of p-NiO/i-Ga 2 O 3 /n-GaN heterojunction diode is nearly 37 times higher than that of p-NiO/n-GaN heterojunction diode. Finally, the working mechanism of the electroluminescence is analyzed in detail through the energy band diagram of the two diodes. [ABSTRACT FROM AUTHOR]

• Near-white LED based on p-CuO/i-CuO/n-GaN was realized by magnetron sputtering and annealing treatment. • CuO could be used as hole injection layer and electron blocking layer under different annealing condition. • The chromaticity coordinates and related color temperatures of the devices were about (0.2381, 0.2606) and 22,505 K. • The i-CuO layer could improve the stability of electron injection and optimize the structure of diode. White light-emitting diodes (WLEDs) have advantages of high efficiency, energy saving, and long working-life, which are ideal choice for next generation of solid-state light sources. Herein we fabricated the near-white light-emitting diode based on the structure of p-CuO/i-CuO/n-GaN heterojunction by magnetron sputtering and annealing treatment. The surface morphology, crystal quality and electrical properties of the CuO layer were investigated by X-ray diffractometer, field emission-scanning electron microscope and Hall measurement. And the influence of the CuO electron blocking layer (EBL) on the diode characteristics were discussed. The current-voltage (I-V) characteristics of those diodes revealed typical p-n junction. Compared with p-CuO/n-GaN heterjunction diode, the EL spectrum of p-CuO/i-CuO/n-GaN heterjunction diode exhibited blue shift and higher intensity. It was found that the addition of CuO EBL enhanced the stability of the diode through analyzing the I-V and EL properties of the diodes. Moreover, at the injection current of 50 mA, the chromaticity coordinates of p-CuO/n-GaN and p-CuO/i-CuO/n-GaN heterojunction diodes are about (0.2686, 0.3334) and (0.2381, 0.2606), and the color temperature are 9205 K and 22,505 K, respectively. Eventually, the EL working mechanism of the two diodes was analyzed in the aspect of the energy band diagram. This study demonstrates the possibility of p-CuO/n-GaN heterojunction with an i-CuO electron blocking layer and their potentials for applications in WLEDs. [ABSTRACT FROM AUTHOR]

With the progressively prominent impact of pollution caused by the extensive use of unsustainable fossil energy on the environment, clean energy with solar energy as an important component is developing rapidly. As a p-type semiconductor material with excellent performance, CuO is expected to become one of the most competitive photovoltaic materials in the field of optoelectronic devices. We first explored the effects of changing the sputtering power on the crystalline quality of CuO thin films, and systematically investigated the crystal structure, surface morphology, optical and electrical properties. Then we fabricated an Au/p-CuO/n-Si/Al heterojunction solar cell by magnetron sputtering and analyzed the influence of the device on the electrical properties at different temperatures. High rectification characteristics typical of diodes were obtained. Finally, by measuring and calculating the photovoltaic performance of the device under simulated sunlight irradiation, we studied the dependence of the device operating temperature on the photoelectric conversion efficiency in detail. • The effect of sputtering power on the physical properties of CuO film was studied. • The CuO film with relatively good quality was obtained by magnetron sputtering. • Device with high rectification characteristics typical based on p-CuO/n-Si structure was prepared. • The operating temperature dependence on the photoelectric conversion efficiency of the device was studied. [ABSTRACT FROM AUTHOR]

With the development of semiconductor technology, ultraviolet light-emitting diodes (UV-LEDs) had been widely used in lighting, sterilisation, biological medical and other fields, which had broad market application prospects. The p-CuO/i-Ga 2 O 3 /n-GaN heterojunction diode was fabricated by radio frequency (RF) magnetron sputtering technology. The influence of ambient temperature on the electrical characteristics of diodes was studied, which exhibited typical diode rectification characteristics with high rectification ratios at different ambient temperatures. It was found that the temperature sensitivity of the forward current was greater than that of the reverse current when the driving voltage were ±3 V. Moreover, two luminescence peaks could be detected by the electroluminescence (EL) measurement, one was a strong ultraviolet (UV) luminescence peak at ∼370 nm, and the other was a wide deep-level luminescence peak at ∼500 nm. Eventually, the luminescence mechanism was discussed from the aspect of the energy band diagram of the heterojunction diode. • Ultraviolet-LED based on p-CuO/i-Ga 2 O 3 /n-GaN heterojunction was prepared. • The Ga 2 O 3 film could be used as an intermediate layer to optimize diode structure. • The diode exhibits excellent electroluminescence characteristics. • At different temperatures, the diode exhibits good electrical characteristics. [ABSTRACT FROM AUTHOR]

• The 25 µm-thick ZnO film using sputtering method was characterized for X-ray detection applications. • p+-Si/ZnO X-ray detector based on the 25 µm-thick ZnO film shows a high sensitivity of 128 μC∙Gy−1∙cm−2 at − 20 V. • The on-off response is related to the V O defect, which was verified by the transmittance spectrum and the TSC spectrum. [Display omitted] In the field of direct-conversion flat panel X-ray detector, semiconductor with thickness of tens to hundreds microns is needed. In this paper, we demonstrate that thick ZnO semiconductor deposited by RF magnetron sputtering can be candidate for the X-ray detector. The 25 µm ZnO film was prepared by sputtering method under 200 °C and a p+-Si/ZnO X-ray detector based on the thick ZnO film was investigated to explore its X-ray detection properties. The detector shows nonzero short circuit current and open circuit voltage indicating the heterojunction nature of the ZnO film in contact with the p+-Si substrate. The detector shows linear response to the X-ray dose rate and has a high sensitivity of 128 μC∙Gy−1∙cm−2 at −20 V under 30 kV p X-rays indicating its great potential in the flat panel X-ray detector applications. The on-off response of the detector is related to the V O defect in the ZnO film, which can be verified from the transmission spectrum, the thermal stimulated current spectrum, and the photoluminescence spectrum. [ABSTRACT FROM AUTHOR]

The good properties of ITO substrate endow the as-grown InN thin films especially attractive for various optoelectronic applications. Herein, the InN thin films were prepared on the ITO substrates by magnetron sputtering. The effects of substrate temperature (T s) on the structural, morphological, and optical properties of InN films were assessed by X-ray diffractometer, scanning electron microscope and ultraviolet–visible spectrophotometer. The combination of structural and morphological investigation suggested that the better InN thin film was obtained at 200 °C. Then, the variation of the optical band gap and transmittance with T s was discussed. What's more, the p-NiO/n-InN heterojunction was trial-produced, and the carrier transport characteristics were studied in the range of 30–120 °C. The heterojunction exhibited excellent I–V characteristics at all operating temperatures. This work enriches the description of InN materials and devices, and provides a useful reference for the practical application of InN. • High-quality InN thin film was obtained on the ITO substrate by magnetron sputtering. • The increase of substrate temperature was conducive to the growth of InN (101) plane. • High rectification ratio diode based on p-NiO/n-InN structure was trial-produced. • The diode also exhibited superior I–V characteristics under high temperature. [ABSTRACT FROM AUTHOR]