Examination of dimensionality for Low Dimensional Conductors Using High Pressure Transport Measurement

我们对一维半导体TiS_3和准二维导体η-Mo_4 O_3得到了下列结果<11>。一维半导体材料TiS_31.我用化学气相输运法确定了生长TiS_3晶体的最佳条件：高温端密封石英管温度为520 ℃，低温端密封石英管温度为480 ℃，起始原料Ti：S = 1：4.2。它的导带中有10^<17>cm^<-3>的本征载流子被某些杂质能级钉扎。在<18><-3>100 K以上，杂质散射占主导地位;而在100 K以上，除了传统的LA声子散射外，还出现了一些散射机制。散射的起源是反常载流子散射，反映了低维能带结构和（或）非反转半导体如GaAs的情况下已知的极性光学声子散射。4.由于室温下的光学活性声子，在295，365，553 cm ^处观察到拉曼谱带<-1>。准二维导体eta-Mo_4 O_<11>1.当沿着eta-Mo_4 O_2的b轴方向施加超过阈值电场时<11>，电荷密度波（CDW）被退钉并对电导有贡献。这说明CDW在准二维导体中的滑动是一维的，而不是二维的。3.这些结果表明，CDW滑动的维数受嵌套矢量对称性的影响，而不是晶体结构的影响。

I have found the following results for one dimensional semiconductor TiS_3 and Quasi two dimensional conductor eta-Mo_4O_<11>.*One dimensional semiconductor TiS_31.I have established the most optimum condition for crystal growth of TiS_3 using a chemical vapor transport technique ; A sealed quartz tube kept at high temperature end is 520ﾟC and low temperature one is 480ﾟC,the ratio of starting materials Ti : S is 1 : 4.2.The TiS_3 is an n-type impurity semiconductor. It has the 10^<17>cm^<-3> intrinsic carriers in a conduction band pinned by some impurity levels. The 10^<18>cm^<-3> donors which make a level at below 24 meV from conduction band minima donate carriers above 100K.3.Below 100 K,the impurity scattering is dominant ; while above 100 K some scattering mechanisms have occurred in addition to a conventional LA phonon scattering. The origin of the scattering are anomalous carrier scattering reflects the low dimensional band structure and (or) polar optical phonon scattering known to the case of the non-inversion semiconductors such as GaAs.4.Raman bands are observed at 295,365,553cm^<-1> due to optical-active phonons at room temperature.*Quasi two dimensional conductor eta-Mo_4O_<11>1.When the electric field beyond a threshold field is applied along the b-axis of the eta-Mo_4O_<11>, the Charge Density Wave (CDW) is depinned and contributes to the electrical conduction.2.In the bc-plane (2-dimensional conduction plane), the CDW slides along the b-axis only. It means that the sliding motion of CDW in these Quasi two dimensional conductor is one-dimensional rather than two-dimensional.3.These results suggest that the dimensionality of CDW sliding is influenced by the symmetry of nesting vector rather than the crystal structure.