Semiconductor-to-metal-transition

Shirotani 1, Kawamura A, Suzuki K, Utsumi W, Yagi T (1991) Insulator-to-metal-to-semiconductor transitions of one-dimensional bis(l,2-dione dioximato)Pt(ll) complexes at high pressures. Bull Chem Soc Jpn 64 1607-1612... 

This salt (NPrQn, /V-propylquinolinium) consists of tetramerized TCNQ chains. It undergoes a phase transition at 220 K which is considered to be a second-order metal-to-semiconductor transition. Optical reflectivity measurements on crystals, with the light polarized in the chain direction, indicate that the charge distribution on the TCNQ sites in the tetrads is less uniform at 100 K than at 300 K. This is as in TEA(TCNQ)2 (see Section III.A.3). However, estimation of this charge distribution from the bond lengths at 300 K [38] gives ambiguous results for this material [63]. 

The electrical conductivity of the material is complex behaving partly like an anisotropic semiconductor and partly like a metal. The metal to semiconductor transition appears to be sample dependent since various workers have reported transition temperatures ranging from 130 to 340 K for samples... 

Angell C., Borick S., Grabow M. (1996) Glass transitions and first order liquid-metal-to-semiconductor transitions in 4-5-6 covalent systems. Journal of Non-Crystalline Solids 205-207, 463-471. 

V2O3 undergoes a metallic-to-semiconductor transition at 168 K. Doping with 1% Fc203 shows that the low-temperature semiconductor phase is antiferromagnetically ordered [57]. Spin relaxation has also been found in a... 

In 1988, the so-called size induced metal insulator transition (SIMIT) was described. [97] It will be observed if the volume of a metal partide is reduced to such an extent that size dependent quantization effects occur. This is the beginning of the metal to semiconductor transition found at the very end of metallic behavior or, coming from the molecular state, the onset of metallic behavior. Hie SIMIT is already effective in 20 nm particles. Due to this quantization effect, standing electron waves with discrete energy levels are formed. 

For the following discussions, the results are conveniently presented according to the interests or emphases of a particular laboratory effort. Much recent work has come from various authors while at the Ames Laboratory. A wealth of information is available for the simplest rare earths (La and Ce) that have no high-temperature phase changes. The reader is directed to an excellent summary of work on the CeH system up to 1985, by Schlapbach et al. (1986a). In early NMR studies by Barnes et al. (1980), a clear transition at about 210 K is attributed to a metal-to-semiconductor transition. Also, a narrow band gap ( 0.01 eV) appears below that temperature, as discussed at some length in sections 6.1 and 6.2. The authors also identify the off-center displacement of o-site atoms. 

Snow, A. W, Wohltjen, H. Size-induced metal to semiconductor transition in a stabilized gold cluster ensemble. Chem Mater 1998,10, 947-950. 

Sb—Bi) [158-160]. Nevertheless, it is surprising that intermediate compositions (Sbi x ASx with X = 0.09 0.40 [161] and Bii- Sb with x = 0.05 0.23 [162]) exhibit semiconducting properties just as does elemental bismuth under pressures of 6 to 24kbar, and Bii, cSb,c (jc= 0.05) alloys under correspondingly lower pressures [158], as if alloying compressed the cell in the same way as does hydrostatic pressure. Possibly a similar metal-to-semiconductor transition might be observed in the system Asi, cPx, which is stable in the As structure up to x = 0.13 under ambient conditions. 

Compression Radial compression was studied via a combined molecular dynamics and density functional theory-based nonequilibrium Green s function approach (Wu et al. 2004). Reversible pressure-induced metal-to-semiconductor transitions of armchair SWNTs were predicted suggesting that SWNTs maybe used as miniature sensitive pressure detectors (Mehrez et al. 2005 Wu et al. 2004). 

Early studies on polycrystalline samples of lanthanum and cerium hydrides by Stalinski (1957b, 1959) indicated that these materials become semiconductors as the trihydride composition is approached. More recent studies on single crystals of cerium hydride by Libowitz and Pack (1969b) showed a sharp increase in resistivity as the hydride composition approached CeH2 illustrated in fig. 26.10. As mentioned in section 5.1, samples in which H/Ce<2.7 showed metallic behavior. However, samples with H/Ce > 2.8 exhibited typical semiconductor behavior with a linear increase in resistivity with reciprocal temperature. Clearly, there is a metal-to-semiconductor transition in cerium hydride at an... 

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