Gu Changzhi

A gas sensor fabricated with field-effect transistors and Langmuir-Blodgett film of porphyrin

LB multilayer films of symmetrically substituted cobalt porphyrins have been deposited on FET and measurements performed on the devices when exposed to the toxic gases NO2, NH3, CO and H2S. Results are presented showing the extreme sensitivity of their IDS to ambient gas such as nitrogen dioxide. The sensitivity of detection was around a few ppm; the qualities are attributed to amplification by the FET and the ordered nature of LB film.

Thermal Conductivity of Diamond-Based Silicon-on-Insulator Structures

Diamond films of various thickness (1-300 μm) were deposited on single-crystal Si active (300 μm) by a microwave plasma chemical vapor deposition method using gaseous mixtures of methane and hydrogen. After thinning of the Si layer by machine and ion-beam polishing a diamond-based silicon-on-insulator structure with final Si layer thickness of about 1 μm is formed. Thermal conductivity of this structure material with various thicknesses of diamond and Si layer was measured. Compared with bulk silicon, the thermal conductivity of the silicon-on-diamond structure with 300 μm diamond and 1 μm silicon increases by 850%.

Effect of Surface Hydrogen Coverage on Field Emission Properties of Diamond Films Investigated by High-Resolution Electron Energy Loss Spectroscopy

The influence of surface hydrogen coverage on the electron field emission of diamond films was investigated by high-resolution electron energy loss spectroscopy. It was found that hydrogen plasma treatment increased the surface hydrogen coverage while annealing caused hydrogen desorption and induced surface reconstruction. Field electron emission measurements manifested that increase of surface hydrogen coverage could improve the field emission properties, due to the decrease of electron affinity of the diamond surface by hydrogen adsorption.

Polishing technology of surface for diamond film using the method of laser ablation

ConclusionGood unity in thickness and a smooth surface of diamond film are obtained by using the methods of laser ablation and machine grind to the surface of diamond film. Compared with the machine polishing method, the polishing rate increased by over 10 times. After laser ablation and machine polishing, the thickness change and the roughness of a diamond film with 400 μm thickness and 1 cm2 area are 10–15 μm and 0.05 μm, and this film is basically suitable to using in electronics.

Factors Influencing Thermal Conductivity in Diamond Film

Diamond films were synthesized on Si substrate by electron-assisted chemical vapor deposition method using gas mixtures of methane (or acetone) and hydrogen. Various crystal structures of diamond films were obtained by synthesis with various deposition conditions. The influences of various deposition conditions on thermal conductivity of diamond film were studied. The results show that large-grain (100)-oriented diamond films synthesized at lower concentration of methane and acetone have higher thermal conductivity, and thermal conductivity increases with the increasing in film thickness and the removal of the SiC layer on the back of the film, at last, annealing in ambience of hydrogen is advantageous to acquiring diamond film with high thermal conductivity.