【作者】 赵春红；

【导师】 赵永年；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2005， 硕士

【摘要】 本论文工作主要是采用一种新的自行设计的磁增强弧光等离子体化学气相沉积法(Magnetron enhanced arc plasma chemical vapor deposition)制备立方氮化硼(c-BN)薄膜及其场发射特性的研究。现已成功地在单晶硅上制备出了含量较高的立方氮化硼(c-BN)薄膜。同时研究了各个沉积参数(基底直流负偏压、弧光等离子体放电电流、气体流量比、沉积时间)对立方氮化硼薄膜的制备及其场发射特性的影响。制备出的薄膜用傅立叶红外(FTIR)光谱和X 射线衍射(XRD)谱来表征。基底负偏压对立方氮化硼薄膜的制备起着及其重要的作用。随着基底负偏压的变化,薄膜中立方相的含量也随之增加。当实验过程中不加任何负偏压时,Cl 对六角相的化学刻蚀就起着至关重要的作用。因此,我们在不加偏压的情况下,又研究了弧光等离子体放电电流、气体流量比以及沉积时间等参数对立方氮化硼薄膜制备的影响。改变弧光放电电流,薄膜中立方相的含量也随之改变。当弧光放电电流增加到某一值时,立方相的含量达到最大值。继续增加放电电流,立方相含量反而降低。改变气体流量比,同样薄膜中立方相的含量也随之改变。研究了立方氮化硼薄膜的场发射特性,发现BN 薄膜表面粗糙度对其场发射的性能有很大影响。当没有施加负偏压时,改变弧光等离子体放电电流、气体流量比以及薄膜厚度等条件,发现立方相含量的多少对其场发射性能也起一定的作用,立方相含量越高,场发射性能越好。最后,利用能带弯曲理论对立方氮化硼薄膜的场发射进行了探讨。更多还原

【Abstract】 Cubic boron nitride (c-BN) having zinc blende type structure has attracted considerable attention because of unique properties. c-BN is a highly promising material for optical, electronic, chemical and mechanical applications, e.g., its hardness being second only to diamond, high thermal conductivity, high chemical and thermal stabilities, lower solubility in ferrous metals as cutting tools than diamond. In comparison to diamond, which is only p-type dopable, c-BN is n-and p-type dopable, therefore suitable to high temperature electronic devices and blue light-emitting diodes. In addition, it is well known that there have emerged many reports on the field emission properties of diamond film due to its characteristics such as high hardness, high heat conductivity, chemical stableness and negative electron affinity(NEA). It is considered an ideal material for field emission cathodes. The III-IV compounds cubic boron nitride(c-BN) have similar properties (NEA, or even better heat conductivity and stableness) to diamond. So a considerable effort has been devoted to development of cold cathodes as a key source for field emission flat panel displays and vacuum microelectronic devices. It is desirable to fabricate cold cathodes which achieve a high emission current operation at a low voltage. Recently, some physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods were employed for synthesizing c-BN films, including plasma-assisted CVD, ion plating, laser deposition, ion beam-assisted deposition and sputtering. For all these methods, energetic-particle bombardment of the substrate was found to be essential for the formation of the cubic phase of boron nitride. However, from the bombardment during film growth, the deposited c-BN films generally exhibited a high compressive stress, which was believed necessary to obtain a cubic phase. The high stress results in a limited maximum film thickness (several hundred nanometers) that can be deposited free from peeling. Up to now, it has not been possible to prepare c-BN films with high quality and sufficient thickness to be identified by Raman spectroscopy. In contrast to be deposition of diamond films, the growth mechanism of c-BN films by the currently successful deposition techniques may be dominated by physical effects at the surface or subsurface region regardless of the PVD or CVD. This difference is possibly due to the lack of an effective chemical reactant as hydrogen does in the diamond growth process by preferentially etching the sp2 components and stabilizing the sp3 structure. In this work, chlorine was introduced into the reactant gases, which was found to be very beneficial for the deposition of c-BN films at a lower or without effective substrate bias. Chlorine was maybe demonstrated to preferentially etch the hexagonal phase during deposition. Hydrogen was found necessary to produce solid boron nitride from gas phase and to balance excessive etching of chlorine. The growth of c-BN films in our system was believed to be a combined process of both chemical effects by chlorine and physical effects by ion bombardment. The chemical effects by chlorine played an important role in the formation of the cubic phase of boron nitride without any substrate bias. Therefore, the residual stress was intensively decreased.Cubic boron nitride films were deposited on silicon substrates by self-made magnetron enhanced arc plasma chemical vapor deposition in an Ar-N2-BCl3-H2 system (BCl3 was diluted 2% in N2 base). By this method, we have successfully deposited the higher c-BN thin film. The characterization of c-BN films was carried out by XRD, FTIR spectroscopy. The effect of direct current bias, plasma discharge current, gas flow ratio, thickness on the formation of c-BN films and field emission characteristics of c-BN ware investigated. The content of c-BN is increased with the increase of DC bias. An absorption band at about 1080cm-1 appears. The c-BN absorption dramatically increases with an increase of the bias voltage. According to the compressive stress model of deposition of c-BN films, the growth of c-BN needs certain stress. When the compressive stress in the films exceeds some a threshold, it accords with the balance condition of c-BN energetics, and commences on accelerating c-BN to form core and then grow. The c-BN content in the film is increased with the increase of stress. The compressive stress in the film due to the bombardment of energetic ions arisen from the substrate bias. The bigger is the substrate bias, the higher is the energy of the bombardment ions. As a result, it causes a bigger stress in the films to form c-BN phase. On the other hand, the chemical effect by chlorine plays some degree role in the formation of the cubic phase of boron nitride;The content of c-BN is increased with the increase of plasma discharge current. When the plasma discharge current enhances to 16A, the content of c-BN reaches a maximum. During deposition, we know that the density of plasma depended on the plasma discharge current. Nevertheless, the sample wasdeposited without substrate bias voltage. So, the chemical effects by chlorine played extreme important role in the formation of the cubic phase of boron nitride instead of relying mainly on ion bombardment. As a result, it can be concluded that the plasma discharge current is also an important factor for synthesizing c-BN;when the ratio of H2 / BCl3(N2)/ Ar was 1:1.5:5, it is to be favorable for the deposition of a high content,When little H2 was injected in the vacuum, it was found it was deficient to produce solid boron nitride from gas phase and to balance excessive etching of chlorine. The field emission characteristics of thin c-BN films were researched in this paper. The influences of deposition parameters on the field emission characteristics of c-BN thin films are very important. The surface morphology of the c-BN film plays an important role in the field emission characteristics of the film. For the films which have rougher surface, electrical field was enhanced because of tip effect. Potential barrier of surface is reduced and thinned, so it’s easier for electron to tunnel into vacuum. Experiment results indicate it have a lower threshold electric field and higher emission current density for sampling which has a rougher surface. With reduce of surface roughness, threshold electric field of c-BN film gets higher. The threshold electric field is 13V/μm, and the emission current density is 224μA/cm2 for c-BN film growth at substrate bias of -175V; Furthermore, the content of c-BN plays some important factor for field emission characteristics. The higher is the content of c-BN, the better is the field emission. The threshold electric field is 8V/μm, and the emission current density is 185μA/cm2 for c-BN film deposited at the arc current of 17A; The threshold electric field is更多还原