【作者】 陈惠娟；

【导师】 薛庆忠；

【作者基本信息】 中国石油大学 ， 材料科学与工程， 2010， 硕士

【摘要】 论文第一部分利用磁控溅射的方法在Si(100)基片上成功沉积了一系列不同结构的非晶碳膜(a-C),对其电输运特性和气体敏感特性进行了较为详细的研究。首先,研究了在室温下NH3对碳纳米薄膜/硅(C/Si)异质结的电容-频率(C-F)特性的影响。主要结果为:在外加频率为50Hz时,当C/Si异质结从空气中转移到盛有少量NH3气体的锥形瓶中(浓度0.2ml/L),异质结的电容迅速地增加到在空气中的230%,改变外加频率,分别为1000、10000、100000Hz时,异质结电容分别增加到在空气中的200%、170%和130%,并提出了相应的理论模型解释了上述现象。研究表明,可以利用C/Si异质结的氨气敏感特性开发氨气传感器。其次,研究了纳米针尖阵列(CNA)结构的制备条件和CNA/Si异质结的酒精气敏特性。其主要结果为:氩气气压对沉积的薄膜表面形貌有着较大的影响,只有在特定的Ar气压下沉积才能形成CNA结构。并且,酒精气体对CNA/Si异质结的电流-电压(I-V)和C-F特性具有显著的影响。尤其对于正向的I-V性质,当正向电压稳定时,将CNA/Si异质结从空气转移到含有少量酒精气体(0.64g/L)的锥形瓶中,其结电阻迅速地减小。经过多次实验发现异质结对酒精气体的敏感度随着薄膜厚度的增加而下降。在外加频率5000Hz下,重复测量酒精气体对异质结电容的影响,实验结果表明当异质结从空气转移到酒精气体中时,异质结的电容值迅速上升,上升到原来的140%,响应时间和恢复时间都非常短。该CNA/Si异质结在酒精气体传感器领域具有潜在的应用价值。最后,研究了在室温下湿度对C/Si异质结电容的影响,选用过饱和盐溶液作为湿度值的标定。主要的实验结果为:在外加频率1000Hz下,当湿度从11%RH变化到95%RH时,该C/Si异质结的电容从～1000pF增加到～3000pF,并且结电容的变化随着湿度的改变呈现着较好的线性关系。研究表明,该C/Si异质结可作为湿度传感器材料。论文的第二部分是用磁控溅射方法制备了纳米碳薄膜和纳米掺钯碳(Pd x C1-x)复合薄膜,并研究了其电学性质。结果表明:掺钯碳膜中含有更高的sp2杂化的碳原子,即在沉积薄膜的过程中,钯诱导sp2杂化的碳结构的形成。并且,掺钯碳薄膜的电阻值比纯碳薄膜下降了3个数量级,即薄膜中掺杂钯显著地提高了薄膜的电导率。还研究了纳米钯碳复合薄膜/硅(Pd x C1-x/Si)异质结对氢气的敏感特性,结果显示PdxC1-x/Si异质结对氢气的敏感度随着纳米掺钯碳薄膜中钯含量x的增加而上升。更多还原

【Abstract】 Ammonia (NH3) sensors based on carbon/sillicon (C/Si) heterojunctions are demonstrated at room temperature (RT). Upon exposure to ammonia (0.2 ml/l) at RT, the interface capacitance of C/Si junction increases dramatically about 230%. The results show that C/Si junctions have high NH3 gas sensitivity, rapid response and high recovery speed at RT. This phenomenon can be attributed to the change of potential barrier width of the junction, which is caused by the adsorption of NH3 molecules. The C/Si junctions can greatly amplify the detection sensitivity of the nano-sized carbon so that the C/Si junctions allow acting as excellent RT gas sensors.Carbon nanotip arrays were grown from silicon substrates via direct current magnetron sputtering at RT. The simple carbon nanotip arrays/n-Si (CNA/Si) heterojunctions were used to detect ethanol gas at RT. The results show that the CNA/Si junctions have high ethanol gas sensitivity, rapid response and high recovery speed at RT. Upon exposure to ethanol gas (0.64 g/L) at RT, the resistance of the junction decreases by 35% at a given positive voltage of 8 V. And the interface capacitance of the junction at 5 kHz can increase by about 40% rapidly when exposed to ethanol gas. The phenomena should be attributed to the change of the Fermi level of the carbon film caused by adsorbing electrons from ethanol molecules. The study shows that the CNA/Si junctions have potential application as ethanol gas sensors.Amorphous carbon (a-C) films were deposited on n-silicon by direct current magnetron sputtering at RT and the corresponding microstructure was characterized. The RT capacitive humidity sensing properties of C/Si junctions were studied by a standard two-probe method. It was shown that with the RH changing from 11 to 95%, a capacitive device response over 200% was achieved at 1 kHz, and the curve of the capacitive response with RH is of high linearity at the given frequency range. The phenomena should be attributed to the change of the Fermi level of carbon film caused by adsorbing electrons from H2O molecules. The result also shows that the capacitance of the junctions increases with decreasing frequency, because the adsorbed water molecules can get stronger polarization at lower frequencies. The study shows that the C/Si junctions have potential application as humidity gas sensors.Using magnetron sputtering method we prepared Pd x C1-x composite films and a-C films on n-Si (100) substrates. Then the electrical properties and the hydrogen sensitive properties of the Pdx C1-x/Si junctions were explored. The results showed that: (1) the palladium-doped carbon films contain higher sp2 carbon structure, induced by palladium atoms, than the pure carbon films; (2) the resistivity of Pdx C1-x films is larger than that of pure carbon films by 3 orders of magnitude; (3) the Pd x C1-x/Si junctions can be used to detect hydrogen gas, because the conductivity of the Pdx C1-x film is sensitive to hydrogen.更多还原