Xili Gao

Ammonia sensitivity of amorphous carbon film/silicon heterojunctions

The amorphous carbon film/n-Si (a-C∕Si) junctions have been fabricated by magnetron sputtering. The results show that these junctions have good rectifying properties and high ammonia (NH3) gas sensitivity. For a given reverse bias voltage, the resistance of the junction can increase by 100 times rapidly when exposed to NH3 gas. This phenomenon may be attributed to the change of the space charge width of the junction, which is caused by the adsorption of NH3 gas molecules. This study shows that these a-C∕Si junctions have potential application as NH3 gas detect sensors.

Influence of chirality on the interfacial bonding characteristics of carbon nanotube polymer composites

The influence of chirality on the interfacial bonding characteristics of single-walled nanotubes (SWNTs) reinforced polymer composites was investigated using molecular mechanics and molecular dynamics simulations. The simulations indicate that the interfacial bonding and shear stress between the SWNT and the poly(methyl methacrylate) depends on the chirality. For SWNTs with similar molecular weights, diameters, and lengths, nanotubes with larger chiral angles achieve higher bonding energy and the armchair nanotube may be the best nanotube type for reinforcement. The general conclusions derived from this work may be of importance in devising advanced nanotube reinforced composites.

Effect of gas pressure on current-voltage characteristics of amorphous carbon film/silicon heterojunction

Amorphous carbon film/n-Si (a-C∕Si) junctions have been fabricated by direct current magnetron sputtering and their current-voltage (I-V) characteristics have been investigated. The results show that the gas pressure has a large effect on the reverse bias I-V characteristics of the junctions. For example, the reverse current can increase by 3300% when the gas pressure decreases from 100000to100Pa. The effect of gas pressure may be attributed to the physisorption process of gas molecules which increases the space charge width and changes the surface states of the junction.

Abnormal I‐V characteristics and metal-insulator transition of Fe-doped amorphous carbon∕silicon p‐n junction

Simple p‐C∕n‐Si junctions have been fabricated by magnetron sputtering at room temperature and their current-voltage (I‐V) characteristics have been investigated. The p‐n junctions show good rectifying properties in a large voltage scope and interesting I‐V characteristics. The most interesting phenomenon observed in these p‐n junctions is that the temperature dependence of some junction resistance shows a metal-insulator transition whose transition temperature is hugely modulated from 162to236K by a bias voltage increasing from 20to40V. This work shows that amorphous carbon films combined with other semiconductor materials can result in some interesting properties that may have potential applications.

Forward tunneling effect and metal-insulator transition in the BaTiO3 film/Si n-n heterojunction

A n-n heterojunction composed of BaTiO3 film and silicon substrate was fabricated, and it shows good rectifying properties in the temperature range of 80–300K. The forward tunneling effect in the junction at low temperatures ( 12V). The temperature dependence of the junction resistance under a high forward field exhibits an electrical field controlled metal-insulator transition. The results were explained by using the band structure of the junction.