Qingfeng Su

CVD diamond alpha-particle detectors with different electrode geometry.

In this paper, two types of detectors, one with a coplanar and the other with a sandwich geometry using an identical CVD diamond film, were fabricated in order to investigate the effects of the film microstructure on the performance of diamond film alpha-particle detectors. An average charge collection efficiency of 42.9% for the coplanar structure and of 37.4% for the sandwich structure detectors was obtained, respectively. Raman scattering studies directly demonstrated that the different counts, collection efficiencies and photocurrents of the two types of detectors mainly resulted from the different micro-structural features between the final growth side and the nucleation side of the diamond film. Under alpha particle irradiation the detector with sandwich geometry had a similar trend on energy resolution with coplanar geometry under different applied electric field. A good energy resolution of 1.1% was obtained for both detectors.

Spectroscopic ellipsometric study of CVD diamond films: modelling and optical properties in the energy range of 0.1–0.4 eV

In this paper, the infrared optical properties of diamond films on silicon substrates grown by means of hot filament chemical vapour deposition (HFCVD) and microwave plasma chemical vapour deposition (MPCVD) method, are studied by infrared spectroscopic ellipsometry (IRSE) in the energy range of 0.1–0.4 eV. The establishment of appropriate models has the strongest influence on the fit of ellipsometric spectra. For diamond films grown by HFCVD method, the best fitting model is Si|diamond| (diamond + void)| air with an 879 nm rough surface layer included by Bruggeman EMA, but for MPCVD film with a 77.5 nm middle layer of SiO2. The average refractive index n of the HFCVD film is about 2.19 and the extinction coefficients k are between 1.0 and 10−3. However, for the MPCVD film, the value of n is very close to that of natural diamond and the k values are about 10−12–10−15, which show that the film grown by MPCVD is transparent in infrared region, and is optically much better than the HFCVD film.

CdTe thin film solar cell on flexible metallic substrate

In this paper lightweight and flexible CdS/CdTe thin film solar cells on metallic substrates have been developed using a close spaced sublimation process with a low deposition temperature. The analysis of basic properties of CdS and CdTe thin films was carried out by SEM and XRD characterization techniques. The thin film solar cell devices were characterized by current- voltage and photocurrent techniques. Open circuit voltage (Voc) of 710 mV, short-circuit current density (Jsc) of 20.55 mA/cm2 and conversion efficiency of 9.04% was obtained for the flexible CdTe/CdS thin film solar cell under AM1.5 illumination.

A New ZnO Film Photodetector Fabricated on Diamond Substrate

Highly c-axis oriented ZnO film was successfully deposited on the nucleation side of free-standing diamond film by RF reactive magnetron sputtering. I-V characteristics of ZnO film photodetector fabricated on diamond substrate were studied under ultraviolet light illumination and a significant photoresponsivity was observed. The dark-current and the photocurrent of the ZnO photodetector operated at 10V are 8.2 nA and 134.8 nA, respectively

Development of MSGC detectors on diamond film-coated silicon composite substrates

In this paper, diamond film-coated silicon was developed to be used as a substrate in a microstrip gas chamber (MSGC) for the first time. The roughness of the composite substrate was rather low, and the resistivity was in the range of 1010?1011??cm. Its capacitance was very small and almost had no variation with frequency. All these results prove that the diamond film/Si composite material is a promising substrate for MSGCs. Using this composite substrate, a MSGC detector with an area of 2 ? 2?cm2 was fabricated. The effects of the drift voltage and cathode voltage on the energy resolution for 5.9?keV 55Fe x-rays have been examined in detail and discussed. An energy resolution (the relative full width at half maximum of the x-ray peak) of 12.3% was achieved when the MSGC was operated at a drift voltage of ?1000?V and a cathode voltage of ?650?V with a gas mixture (90% Ar + 10% CH4).

Preparation and characterization of [100]-oriented diamond films by HFCVD

In this paper we report high quality [100]-oriented diamond films prepared by HFCVD using hydrogen as carrier gas and C2H5OH as carbon source for the first time. The surface morphology observed by SEM showed polycrystalline diamond films with [100] faced structure with an average grain size of ~20 μm. The Raman spectrum indicated sp3 bonding with a sharp peak at 1333 cm-1. The I-V characteristics obtained via Au contact were determined by semiconductor characterization system. The electrical resistivity of HFCVD [100]-oriented diamond film was ~3.0x1010Ω cm. The capacitance and dielectric loss of films were very small with the value of 2.0pF and 0.02, respectively, and almost had no dependence with the change of frequency in high frequencies.

Effects of texture on the properties of polycrystalline HgI2 films

Due to different oriented polycrystalline HgI2 films show different properties. In this paper the properties of different oriented HgI2 films have been investigated by scanning electron microscopy, X-ray diffraction and current-voltage measurements. The measured results indicate HgI2 films are of high quality and the properties of the (001)-oriented HgI2 film are better than those of the free oriented ones. The dark current of the (001)-oriented HgI2 film is 0.5 nA with an applied bias voltage of 40 V. The current of (001)-oriented HgI2 film keeps unchanged during measurement.

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.

Optical Characteristics of Nano-crystalline Diamond Films as X-ray Lithography Masks for Integrated Circuit Fabrication

In this paper, the structure, morphology and optical properties of nano-crystalline diamond (NCD) films, deposited by hot-filament chemical vapor deposition (HFCVD) method under different carbon concentration, are investigated. With increasing the carbon concentration during the film deposition, the diamond grain size is reduced and thus a smooth diamond film can be obtained. According to the data on the absorption coefficient in the wavelength range from 200 to 1100 nm, the optical gap of the NCD films decreases from 4.3 eV to 3.2eV with increasing the carbon concentration from 2.0% to 3.0%

Studies on coplanar radiation sensor based on diamond film

An X-ray diamond film sensor with coplanar electrode geometry was fabricated and an average charge collection efficiency of 45.8% at an applied electric field of 66.7kV/cm was obtained. Scanning electron microscopy and Raman scattering studies directly demonstrated that the different collection efficiencies of the coplanar and sandwich sensors mainly resulted from the different micro-structural features between the final growth side and the substrate side of the diamond film. The energy resolution of the diamond sensor significantly decreased with the applied electric field. A good energy resolution of 1.55 % was obtained at 66.7kV/cm for the coplanar diamond film sensor