掺磷四面体非晶碳薄膜的电学性能

ELECTRICAL PROPERTIES OF PHOSPHORUS INCORPORATED TETRAHEDRAL AMORPHOUS CARBON FILMS

采用过滤阴极真空电弧技术以PH_3为掺杂源,施加0—200 V基底负偏压,制备了掺磷四面体非晶碳(ta-C:P)薄膜,利用X射线光电子能谱(XPS)和Raman光谱研究ta-C:P薄膜的微观结构,通过测定变温电导率和电流-电压曲线,考察ta-C:P薄膜的导电行为。结果表明,磷掺入增加了薄膜中sp^2杂化碳原子含量和定域电子π/π~*态的数量,提高了薄膜的导电能力,且以-80 V得到的ta-C:P薄膜导电性能最好,在293—573 K范围内ta-C:P薄膜中的载流子表现出跳跃式传导和热激活传导两种导电机制,电流-电压实验证明ta-C:P薄膜为n型半导体材料。

Great attention has been given to diamond-like carbon（DLC） or tetrahedral amorphous carbon（ta-C） films due to their potential applications in electronic devices as semiconductor materials.The controlled variation of electrical conductivity through doping is of primary importance. Active phosphorus element could be introduced into ta-C films to achieve n-type doping and the resulted films show potential applications as photovoltaic solar cells,semiconductor field emitters or biomedical coatings.However,an inconsistency of doping effect and graphitization of the bonding still exists in the role of phosphorus atoms in carbon films.A detailed study on the conduction mechanism related to the structural changes should be attempted to further understand the conductive behavior of the films.Based on this purpose,phosphorus incorporated tetrahedral amorphous carbon （ta-C：P） films were deposited using filtered cathodic vacuum arc technology with PH_3 as a dopant source under negative substrate biases of 0--200 V.The structural characteristics of ta-C：P films were investigated by X-ray photoelectron spectroscopy（XPS） and Raman spectroscopy,and the electrical behaviors of the films were examined by measuring electrical conductivity at the temperature range of 293-573 K and current-voltage curves.Results indicate that phosphorus implantation enhances the contents of sp^2 sites in ta-C films and the numbers of localized electronicπandπ^ states as hopping sites,and improves the conductive ability of the films.ta-C：P film obtained at-80 V shows the best conductive property.The carriers of ta-C：P films represent the hopping conduction in localized band tail states and the thermally activated conduction in extended states in the temperament range of 293-573 K.The results of current-voltage curves indicate that ta-C：P films are n-type semiconductor materials.