氮化钽薄膜的结构和电输运性质研究

发布时间：2018-08-27 06:30

【摘要】：面心立方结构的δ-TaNx材料因其优越的物理、化学及机械性能(如高硬度、耐磨、化学惰性、热稳定性以及低的电阻温度系数),现已在耐磨涂层、薄膜电阻以及集成电路中的扩散势垒等领域得到了广泛应用。另外,δ-TaNx薄膜又具有较高的超导转变温度(6-10.5 K)、较小的超导带隙(~1.24 meV)及低的费米面态密度等特点,因而在下一代超导纳米线单光子探测器、金属-绝缘体-超导体隧道结器件等领域有着潜在的应用前景。本论文通过射频磁控溅射的方法,采用TaN靶,在石英玻璃基底上成功制备了系列面心立方结构的多晶δ-TaNx薄膜,对薄膜的晶体结构、微观形貌、电学性质进行了系统研究,分析了溅射条件对薄膜结构和电输运性质的影响,并对δ-TaNx薄膜在不同温区的导电机制进行了探讨。在石英玻璃上通过改变基底温度生长了系列面心立方结构的δ-TaNx多晶薄膜,X射线衍射及扫描电镜形貌结果显示,薄膜的平均晶粒尺寸随基底温度的升高逐渐增大。电输运测量结果表明,δ-TaNx薄膜在~5 K以下表现出类似超导体-绝缘体颗粒膜的电输运性质;随着温度的升高,薄膜在10-30 K表现出类似金属-绝缘体颗粒膜的性质;在70 K以上,热涨落诱导的遂穿(FIT)导电机制主导着电阻率的温度行为。因此,多晶δ-TaNx薄膜的类颗粒膜属性使其具有较高的电阻率和负的电阻温度系数。在石英玻璃上通过改变氮分压生长了系列δ-TaNx薄膜,X射线衍射结果显示薄膜为面心立方结构。扫描电镜形貌表征显示δ-TaNx薄膜具有类颗粒膜属性,并且随氮分压的增加,薄膜的结晶质量逐渐变差,平均颗粒尺寸逐渐减小。电输运测量结果表明:在~5 K以下温区,随着氮分压的增加,薄膜的绝缘体-超导转变现象逐渐消失。在~10以上温区,薄膜的电阻率与温度的关系存在明显差异。对于在0.2%、0.4%、0.94%氮分压下制备的δ-TaNx薄膜,在10-350 K整个温区的电输运行为由FIT导电机制主导;而对于5.39%和7.50%氮分压下制备的δ-TaNx薄膜,在50 K以下的导电行为可用Mott的变程跳跃模型描述,而在50 K以上,FIT导电机制仍主导样品的导电行为。
[Abstract]:Due to its superior physical, chemical and mechanical properties (such as high hardness, wear resistance, chemical inertia, thermal stability and low resistance temperature coefficient), 未 -TaNx materials with face-centered cubic structure are now being used in wear-resistant coatings. Thin film resistors and diffusion barriers in integrated circuits have been widely used. In addition, 未 -TaNx thin films have the characteristics of high superconducting transition temperature (6-10.5 K), small superconducting band-gap (1.24 meV) and low Fermi surface state density, so they are used in the next generation superconducting nanowire single-photon detectors. Metal-insulator-superconductor tunneling devices have potential applications. In this paper, a series of polycrystalline 未 -TaNx thin films with face-centered cubic structure have been successfully prepared on quartz glass substrate by RF magnetron sputtering and TaN target. The crystal structure, microstructure and electrical properties of the films have been systematically studied. The effects of sputtering conditions on the structure and electrical transport properties of 未 -TaNx thin films were analyzed, and the conduction mechanism of 未 -TaNx films at different temperatures was discussed. A series of 未 -TaNx polycrystalline films with FCC structure were grown on quartz glass by changing substrate temperature. The results of X-ray diffraction and SEM show that the average grain size of the films increases with the increase of substrate temperature. The results of electrical transport measurements show that 未 -TaNx films exhibit the same electrical transport properties as superconductor-insulator granular films below 5 K, and at 10-30 K, the films exhibit the properties similar to those of metal-insulator granular films at 10-30 K, and above 70 K, the films exhibit the properties similar to those of metal-insulator granular films at 10 ~ (-30) K. The thermal fluctuation induced tunneling (FIT) conduction mechanism dominates the temperature behavior of resistivity. Therefore, the particle like properties of polycrystalline 未 -TaNx film make it have high resistivity and negative resistance temperature coefficient. A series of 未 -TaNx thin films have been grown on quartz glass by changing the nitrogen partial pressure. The X-ray diffraction results show that the films are of face-centered cubic structure. The SEM results show that 未 -TaNx films have the properties of granular films. With the increase of nitrogen partial pressure, the crystalline quality of 未 -TaNx films becomes worse and the average particle size decreases. The results of electrical transport measurements show that the insulator-superconducting transition of the films disappears with the increase of nitrogen partial voltage in the temperature range below 5 K. In the temperature range above 10, the relationship between the resistivity and the temperature of the film is obviously different. For 未 -TaNx films prepared at 0.2and 0.94% nitrogen partial pressure, the electrical transport behavior in the whole temperature region of 10-350K is dominated by the conduction mechanism of FIT, while for 未 -TaNx films prepared at 5.39% and 7.50% nitrogen partial pressure, the conduction behavior below 50 K can be described by the variable path jump model of Mott. However, the conduction mechanism of fit still dominates the conduction behavior of the sample at 50 K or above.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ135.13;TB383.2

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