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Influence of Chemical Composition of Liquid Phase and Growth Process on Physical Properties of Bi_2Se_3, Bi_2Te_3 and Bi_2Te_2Se Compounds

100%

Hruban A. , Materna A. , Dalecki W. , Strzelecka G. , Piersa M. , Jurkiewicz-Wegner E. , Diduszko R. , Romaniec M. , Orłowski W.

Acta Physica Polonica A

2011

tom 120

nr 5

950-953

We studied synthesis and crystal growth of Bi_2Te_3, Bi_2Se_3 and Bi_2Te_2Se compounds by means of vertical Bridgman method. Crystals were grown from stoichiometric melts and under different molar ratio of Bi:Te, Bi:Se or Bi:Te:Se. The obtained crystals were characterized by X-ray diffraction analysis, energy dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy, and the Hall effect measurements. Some of the samples demonstrated insulating bulk behavior, by means of resistivity versus temperature measurements.

Ac electrical parameters of Al-ZnPc-Al organic semiconducting films

72%

Kitaneh R. , Saleh A. , Gould R.

Open Physics

2006

tom 4

nr 1

87-104

The ac electrical parameters of thermally evaporated zinc phthalocyanine, ZnPc, semiconducting thin films was measured in the temperature range of 180–390 K and frequency between 0.1 and 20 kHz. Aluminum electrode contacts were utilized to sandwich the organic ZnPc semiconducting films. Capacitance and loss tangent decreased rapidly with frequency at high temperatures, but at lower temperatures a weak variation is observed. An equivalent circuit model assuming ohmic contacts could qualitatively and successfully explains capacitance and loss tangent behavior. The ac conductivity showed strong dependence on both temperature and frequency depending on the relevant temperature and frequency range under consideration. Ac conductivity σ (ω) is found to vary with ω, as ω s with the index s ≤ 1.35 suggesting a dominant hopping conduction process at low temperatures (< 250 K) and high frequency. The conductivity of some samples did not increase monotonically with temperature. This behavior was attributed to oxygen exhaustion of the sample as its temperature is increased. The ac conductivity behavior at low temperatures of ZnPc films could be described well by Elliott model assuming hopping of charge carriers between localized sites.