Run Xu

Growth of p-type ZnO films and fabrication of ZnO photodiode-based UV detectors

In this work, Al–N-co-doped ZnO films were deposited on the smooth nucleation side of a freestanding diamond film by a radio-frequency (RF) reactive magnetron sputtering method. The influence of sputtering atmosphere and substrate temperature on the conduction type of ZnO films was studied. ZnO photodiodes were fabricated by depositing the Al–N-co-doped p-type ZnO films on the Al-doped n-type ZnO films. The ZnO photodiode exhibited the distinct rectifying current–voltage (I–V) characteristics with a turn-on voltage of ~2.0 V. The photodiode was used for UV detector application and the detector showed a significant discrimination between UV and the visible light.

Effect of a buffer layer on the properties of UV photodetectors based on a ZnO/diamond film structure

In this paper, ZnO films were grown on the nucleation sides of freestanding diamond substrates with and without a ZnO homobuffer layer by the radio-frequency (RF) magnetron sputtering method. The effects of buffer layers on the properties of the ZnO film and UV photodetectors based on a ZnO/freestanding diamond film structure were studied. The experimental results suggested that the buffer layer was helpful in improving the crystalline quality of ZnO/diamond heteroepitaxial films and the electrical property of the ZnO photodetectors was relative to the crystalline quality of ZnO films. For the photodetector based on the ZnO film with a buffer layer, a higher value of photo-responsivity under a 10 V bias voltage and a better time-dependent photocurrent characteristic were obtained.

A nanocrystalline CVD diamond film as an x-ray radiation detector

In this work, an x-ray radiation detector was developed from a nanocrystalline diamond (NCD) film. The NCD film, with a grain size of about 20 nm and a thickness of ~5 µm, was deposited on a silicon substrate using a hot-filament chemical vapour deposition (HFCVD) method. The response to radiation and the energy resolution at room temperature of the obtained metal-NCD/Si-metal detector were investigated using 5.9 keV x-rays from a 55Fe source. With an electric field 50 kV cm−1, this detector showed a dark-current of ~5.88 µA, and under x-ray illumination a net response current of ~576 nA and an energy resolution of ~22.7%. It was also shown that the energy resolution deteriorated when the diamond grain size was reduced.

The growth of Si overlayers on Er2O3(111)/Si (111) by solid phase epitaxy

The Si overlayers were grown by solid phase epitaxy on the atomically smooth Er2O3 (111) films, which is prepared on the Si (111) substrate in optimum conditions. The twin structure was observed in the spot-like reflective high energy electron diffraction (RHEED) patterns. The rough surface of Si overlayer, as identified by both RHEED results and Atomic force microscopy (AFM) images, indicated a three dimensional growth mode in contrast to the two dimensional growth mode of Er2O3 on the Si (111) substrate. The physical origin of three dimensional grow is given based on the interfacial energy argument.

Effects of Annealing in N2 and Air after CdCl2 Treatment on the Properties of CdS Thin Films

The influence of annealing under different conditions on CdS films after CdCl2 post-growth treatments was investigated. The crystalline quality of CdS films was improved after the treatment with CdCl2 at 400°C in N2.

Preparation and Properties of N-ZnS Film/P-Si Heterojunction

ZnS films were prepared on silicon (Si) and glass substrates by radio-frequency (RF) magnetron sputtering method. The effect of annealing treatment on the structural and optical properties of ZnS films was studied. The results showed that annealing treatment was helpful in improving the crystalline quality of the ZnS films, and the bandgap was about 3.61eV and 3.49eV for films with and without annealing, respectively. A ZnS/ Si heterojunction diode was fabricated successfully by depositing ZnS films on p-type single-crystalline Si substrates. The electrical and optical property of the device was reported.

Heterojunction fabricated by deposition of ZnO films on boron-doped nanocrystalline diamond film

Boron-doped p-type nanocrystalline diamond (NCD) films were grown by microwave plasma chemical vapor deposition (MPCVD) method via introduction of the gas mixtures of methane, hydrogen and diborane. The effects of B/C ratios of gas mixtures on the electrical properties of NCD films were investigated by Hall effect measurement system. N-type ZnO films were prepared on NCD films by radio-frequency (RF) magnetron sputtering method. The dependence of electrical resistivity and carrier concentration of ZnO thin films on oxygen partial pressure was studied. In addition, I-V characteristic of the n-ZnO / p-NCD heterojunction was measured. The results showed a rectifying behavior of this structure.

Study on the neutron detector based on (100)-oriented diamond film

A neutron detector is developed by evaporating a layer of ¹⁰B on (100)-oriented diamond film. At the electric field of 1 V/μm, the energy resolution is 9.3%, the detecting efficiency to²⁵²Cf neutron is 1.67%.

The electrical properties of the diamond optoelectronic device

200 εm thick free-standing polycrystalline diamond films were grown by microwave plasma chemical vapor deposition (MPCVD) method. The nucleation surfaces of diamond were characterized by XRD, Raman scattering, atomic force microscopy (AFM) method. An ultraviolet (UV) optoelectronic device was fabricated on diamond nucleation surface, showing clear modulation of channel current.

STUDIES ON THE HETEROJUNCTION STRUCTURE OF n-Si/p-NANOCRYSTALLINE DIAMOND FILM

An undoped p-type nanocrystalline diamond (NCD) film was grown by an electron assisted hot filament chemical vapor deposition (EA-HFCVD) technology on an n-type single-crystalline Si substrate to fabricate p-NCD/n-Si heterojunction. The structure and morphology of the NCD film, which was analyzed by Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), showed that the film consisted of 40–60 nm polycrystalline nano-grains. The results showed that with EA-HFCVD method, not only an undoped NCD film with high conductivity but also a p–n heterojunction diode between the NCD film and n-Si substrate was fabricated successfully. The p-NCD/n-Si heterostructure was also used for ultraviolet (UV) photodetector application. Operating at a bias voltage of 10 V, this photodetector showed a significant discrimination between UV and visible light, and the UV/visible-blind ratio was about three orders of magnitude.