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

对一维半导体TiS_3和准二维导体ETa-Mo_4O_(11)及准二维导体Eta-Mo_4O_(11)的研究结果表明：一维半导体TiS_3晶体生长的最佳条件是采用化学气相输运技术，高温端的密封石英管温度为520ﾟC，低温石英管为480ﾟC，原料配比为1：4.2。它在由某些杂质能级钉扎的导带中有10^&lt；17&cm；-3&gt；本征载流子。导带极小值能级在24 meV以下的10^-lt；18；-3&gt；施主在100K以上以杂质散射为主，而在100K以上，除了传统的LA声子散射外，还发生了一些散射机制。散射的起源是反常载流子散射，反映了非反转半导体如GaAs的低维能带结构和(或)极性光学声子散射。4.在室温下，由于光学活性声子的作用，在295,365,553 cm^&1&gt；处观察到拉曼频带。2.在BC面(二维导电面)，电荷密度波只沿b轴滑动。这意味着CDW在这些准二维导体中的滑动运动是一维的，而不是二维的。3.这些结果表明，CDW滑动的维度受嵌套矢量对称性的影响，而不是晶体结构。

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.