WO<sub>3</sub> thin films have been widely studied because they exhibit the electrochemistry effect i.e. a reversible change of color when in contact with an electrolyte and under bias or light illumination which can be used in smart windows and displays. In this work, the optical properties of tungsten oxide films prepared by DC reactive magnetron sputtering and sol-gel method were investigated. The transmittance of the samples was investigated by double-beam UV-VIS-NIR spectrophotometer respectively. The transmittance of the samples changed greatly with wavelength in the range from 250nm to 350nm and was a minimum at about 280nm. The transmittance of samples prepared by sol-gel is better than that by DC reactive magnetron. Molecular structure and surface morphology of samples were obtained by AFM. Film materials prepared by DC reactive magnetron sputtering method are evener and compacter than those by sol-gel method. The molecular of sample by sol-gel is obvious tetrahedron and the molecular of sample by DC reactive magnetron tends to be planar constructure. The chemical bonds of W-O and O-O of the samples are about 0.5nm and 0.6nm long respectively.
The light-emitting properties based on ladder-type poly (P-Phenylene) (LPPP) with carbon nanotubes were investigated. The light-emitting devices with the heterostructure are consisted of the hole transporter LPPP and the electron transporter Alq3. Carbon nanotubes of 1 wt % were added in LPPP. The microcavity effect could be achieved by adjusting organic layers between Au and Al electrodes. It was also found that the light emission intensity was further increased and the emission peak was narrowed after doping carbon nanotubes as compared with that of samples without carbon nanotubes. This may be ascribed to increasing conductivity and mobility of organic lagers via doping carbon nanotubes.
In this paper, the field electron emission from carbon nanotubes on oriented growth diamond films was investigated. Carbon nanotubes and orientation growth diamond films were prepared by hot filament and microwave plasma CVD. The samples obtained were characterized by scanning electron microscopy and Raman spectroscopy. The field emission experiments were performed in an ion-pumped vacuum chamber for different samples. The experimental results have shown that the field emission properties of carbon nanotubes films/diamond films structure have greatly been improved. A turn-on field of 0.9 V/μm and a maximum current of 500μA at 1.5/μm were observed. A lower turn-on field of 0.7V/μm was achieved after chemical treatment. This improvement may be attributed to the tiny tip shape of the carbon nanotubes on diamond films, which provided an additional local increase in electric field at the tip end.
The light-emitting properties based on ladder-type poly (P-Phenylene) (LPPP) with carbon nanotubes were investigated. The light-emitting devices with the heterostructure are consisted of the hole transporter LPPP and the electron transporter Alq<sub>3</sub>. Carbon nanotubes of 1 wt % were added in LPPP. The microcavity effect could be achieved by adjusting organic layers between Au and Al electrodes. It was also found that the light emission intensity was further increased and the emission peak was narrowed after doping carbon nanotubes as compared with that of samples without carbon nanotubes. This may be ascribed to increasing conductivity and mobility of organic lagers via doping carbon nanotubes.
The current-voltage properties of CdS/CdTe heterojunction were first discussed under ideal conditions (without any losses). Conversion efficiency of CdS/CdTe heterojunction solar cells was then investigated under AM1.5 illumination. The results showed that the conversion efficiency of solar cells could be achieved up to 27%, which was in agreement with the results predicted previously. Meanwhile, the realistic conversion efficiency of CdS/CdTe heterojunction solar cells was about 23% after taking into consideration of influence of some material parameters. Given considerable progress that has been made in manufacturing CdS/CdTe solar cells in recent years as well as considering a rational theoretical analysis, the conversion efficiency of 23% is achievable in the near future.
The ultraviolet light emission from diamond films was investigated. The diamond films on Si (100) were deposited by microwave plasma chemical vapor deposition. The B-doped and P-doped layers were formed by cold ion implantation. The properties of p-type and n-type layers were characterized by SEM, SIMS, Raman spectroscopy and Hall measurements. The experimental results showed that a sharp emission peak at 235nm was observed at 22V for 9niA at room temperature. A broad A-band emission in the visible region was also appeared simultaneously. The intensity of ultraviolet emission was changed with carrier mobility and temperature. The results obtained have discussed in detail.
The microcavity light emitting devices were fabricated based on ladder-type poly (p-phenyline) (LPPP) and doped tris (8- hydroxyquinoline aluminum Alq<SUB>3</SUB>) heterojunction structure. The light emitting layers we LPPP with hole transportation and Alq<SUB>3</SUB> as electron transporter. ITO and AL were the hole and electron injecting. Experimental results showed that the microcavity effect has been achieved simply by adjusting thickness of the organic light emitting layers between the ITO and AL electrodes. The stability of the microcavity devices with the heterojunction structure based on LPPP and doped- Alq<SUB>3</SUB> was greatly improved. This can be ascribed to that the ladder-type structure of LPPP exhibited a higher thermal and chemical stability, and the intermolecular hydrogen bonding between the depant molecules was eliminated, led to decreasing nonvadiative centers.
The diamond-based photodetectors were investigated. The diamond films were synthesized by microwave plasma assisted chemical vapor deposition. The films were characterized by scanning electron microscopy and Raman spectroscopy etc. The photodiode structures were fabricated on the free standing diamond films. The experimental results showed that the devices exhibited a strong UV photoresponse. It was found that the structures of the diamond films have a significant effect on the performance of the devices. The photoconductive gain of heteroepitaxial diamond films was greater than that of polycrystalline diamond films.
Based on the single electron Hartree-Fock appropriation and extended-ions method, the optical absorption and emission properties of F-center-OH defect pairs (F<SUB>H</SUB>(OH)) is CsCl, CsBr and CsI were investigated in which a polar effect of F- center electron in excited state was considered. The calculated results show the association of F-center and OH substitution ions on (100) next-nearest-neighbor positions in CsCl, CsBr, and CsI forms a new stable defect F<SUB>H</SUB>(OH). The neighboring OH ion splits the pure F-center absorption band into widely separated F<SUB>H</SUB>(1) and F<SUB>H</SUB>(2) electronic absorption polarized parallel and perpendicular to the pair axis. Moreover, the neighboring OH ion quenched the emission in CsCl, but creates strong emission in CsBr and CsI. The theoretical results were in good agreement with the experimental data. A possible mechanism was presented to explain the emission in CsBr and CsI but quenched in CsCl.
The nucleation and growth of diamond by laser ablation were investigated by scanning electron microscopy and Raman spectrum. The laser deposition parameters have a significant effect on the quality of diamond. High quality of diamond can be achieved by laser deposition with the wavelength of 193 nm, whereas only amorphous carbon higher than 193 nm. Experimental evidences showed that a negative bias voltage relative to the target was applied to substrate, greatly led to nucleation enhancement by ion bombardment. In addition, the stress-induced phase transformation from non-diamond to diamond was occurred by ion bombardment during the nucleation process.
In this article, the properties of WC-SiC-Co and WC-B<SUB>4</SUB>C- SiC-Co coatings on 20<SUP>#</SUP> carbon steel surfaces by using a continuing CO<SUB>2</SUB> laser with an output power of 2 kw were investigated. The physical phases in alloy lasers were analyzed, and their hardness distribution and anti-abrasion property were tested. The experimental results showed that the hard alloy materials with high quality can be deposited on the carbon steel surface with low cost, fully changed the chemical compositions of the steel surface, and greatly enhanced the hardness and anti-abrasion of the steel surfaces.