CVD法制备硫化钨、硫化钼钨二维材料光学性质及其场效应晶体管器件特性研究

发布时间：2018-06-20 12:57

本文选题：化学气相沉积 + 单层硫化钨　；参考：《深圳大学》2017年硕士论文

【摘要】：自2004年发现石墨烯以来,原子层厚度的二维材料由于其独特的电学和光学性质而引起了广泛的兴趣。过渡金属硫族化合物二维材料展现了许多石墨烯所不具有的物理特性,广泛研究表明其在晶体管、光探测器、光伏电池等方面具有极大的应用前景。本论文面向二维材料硫化钨的可控制备与三元合金硫化钼钨,重点研究了硫化钨二维材料的气相生长工艺,以及单层硫化钼钨的光学特性与场效应晶体管性能。主要内容和结果如下:(1)采用化学气相沉积法(CVD)成功制备出尺度约为20 μm、厚度约为0.95 nm的单层WS_2,通过对实验制备的单层与多层硫化钨拉曼光谱对比发现,单层WS_2的A1g振动模式明显强于E_(2g)~1振动模式,随着层数的增加,E_(2g)~1振动模式会发生红移,A1g振动模式会发生蓝移,两种振动模式间距增大,这是由于在较厚的样品中存在。通过对光致发光谱测试分析,发现单层WS_2光致发光特征峰的峰强明显强于多层。对WS_2热稳定性研究发现随着温度的变化,A1g振动模式的改变明显大于E_(2g)~1,这是由于Ag振动模式具有更强的-声子耦合。通过对单层Mo(1-x)W_xS_2变温PL分析发现,由于温度变化出现晶格膨胀效应,带隙宽度会随之改变。(2)利用CVD方法通过在硫化钨生长中掺入钼元素的方式制备合金化的单层Mo(1-x)W_xS_2。同时证明了用Raman光谱手段可以准确地区别三元合金和异质结,通过光致发光谱测试分析,我们证明了通过这种方式可以将掺入Mo的合金化单层Mo(1-x)W_xS_2带隙从1.82eV(MoS_2)到1.95eV(WS_2)精细调控,从而满足不同功能的需求。由于PL峰位对掺杂浓度非常敏感,因此可以通过测量三元合金Mo(1-x)W_xS_2的PL峰位的偏移幅度反向推算掺杂浓度,由此计算出我们制备的Mo(1-x)W_xS_2组分x为0.68。通过在变温拉曼光谱测试分析,我们得出由于三元合金Mo(1-x)W_xS_2具有低的自由能和内部能量,因此热稳定性好。(3)通过传统的微加工工艺手段制备了具有高开关比(～105)的背栅Mo(1-x)W_xS_2场效应晶体管,在不同温度(20 K-300K)下测量电学性能时,没有非常清楚地观察到金属绝缘体转变(MIT),通过研究分析,原因在于电子电荷浓度较低(小于1×1013cm-2)和栅极扫描电压有限(小于70V),因为当测试电压超过70 V就会被击穿。通过对单层Mo(1-x)W_xS_2场效应晶体管进行变温输运性能测试,数据与输运模型有较好的吻合度,高温段(80 K)载流子以热激发方式迁移,低温段(80K)载流子在局部区域跳跃传输。对电荷散射机制研究发现,在低于80 K的低温段,随着温度的降低,迁移率会单调增加,最后由于库伦散射限制达到饱和值,在300 K的时候迁移率约为30 cm~2V~(-1)s~(-1)。
[Abstract]:Since the discovery of graphene in 2004, two-dimensional materials with atomic layer thickness have attracted wide interest due to their unique electrical and optical properties. The two-dimensional materials of transition metal sulfur compounds exhibit many physical properties which graphene does not possess. Extensive research shows that they have great application prospects in transistors photodetectors photovoltaic cells and so on. In this paper, the controllable preparation of tungsten sulfide and the ternary alloy molybdenum tungsten sulfide were studied. The gas phase growth process of tungsten sulfide, the optical properties of monolayer molybdenum tungsten sulfide and the properties of field effect transistors were studied. The main contents and results are as follows: (1) single layer WS2 with a scale of about 20 渭 m and a thickness of about 0.95 nm was successfully prepared by chemical vapor deposition (CVD). The Raman spectra of monolayer and multilayer tungsten sulfide were compared with each other. The A1g vibration mode of the single layer WS2 is obviously stronger than that of the ESP 2g / 1 vibration mode. With the increase of the number of layers, the red shift A1g vibration mode will occur and the distance between the two vibration modes will increase, which is due to the existence of the thick sample. By analyzing the photoluminescence spectrum, it is found that the peak intensity of the characteristic peak of single-layer WSS _ 2 is obviously stronger than that of multi-layer. The thermal stability of WS2 is studied. It is found that the change of vibration mode of A1g with the change of temperature is obviously larger than that of ESP 2g / 1, which is due to the stronger phonon coupling of Ag vibration mode. Based on the analysis of the variable temperature PL of single layer Moan1-xS2, it is found that because of the lattice expansion effect, the band gap width will change with the change of temperature.) the alloyed monolayer Mo _ (1-x) W _ xS _ 2 was prepared by doping molybdenum into the growth of tungsten sulfide by CVD method. At the same time, it has been proved that ternary alloys and heterostructures can be distinguished accurately by Raman spectroscopy. By means of photoluminescence analysis, we have proved that the alloyed monolayer Moan1-xS2 doped with Mo can be controlled by fine regulation from 1.82 EV / MoS2 to 1.95 eVWSVI / 2). In order to meet the needs of different functions. Because the PL peak is very sensitive to the doping concentration, the doping concentration can be calculated backwards by measuring the PL peak offset of the PL peak of the ternary alloy Mohl-xS-2, and the calculated x of our prepared Mo-1-xS-2 WxS2 component is 0.68. Based on the Raman spectroscopic analysis at variable temperature, we find that because of the low free energy and internal energy of the ternary alloy Moan1-xTiW _ xS _ 2, Therefore, thermal stability is good, and the back gate Moan1-xWxS2 FET with high switching ratio (105) has been fabricated by traditional micromachining technology. When measuring electrical properties at different temperatures (20K-300K), The metal insulator transition is not observed very clearly, due to the low electron charge concentration (less than 1 脳 1013cm-2) and the limited grid scan voltage (less than 70V), because when the test voltage exceeds 70V, it will be broken down. By testing the variable-temperature transport performance of single-layer Moan1-xS2s, the data are in good agreement with the transport model. The high temperature section of 80K) carriers migrate in a thermally excited manner, and the low-temperature section of the carrier hops in the local region. It is found that at low temperature below 80 K, the mobility increases monotonously with the decrease of temperature. Finally, due to the limit of Coulomb scattering reaching saturation value, the mobility is about 30 cm ~ (2) V ~ (-1) ~ (-1) ~ (-1) ~ (-1) at 300 K.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN386;TQ136.1

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