Saturation and quantum oscillations in the magneto-seebeck-effect of p-type Bi2Te3

The high magnetic field saturation values of the thermoelectric power between 20 and 80 K of heavily doped p-type Bi₂Te₃ can be accounted for quantitatively by a two-valence-band model.     

Reaction of certain isocyanates with azomethines. Evidence for a new heterocyclic adduct

The preparation of triazinone (I) from certain isocyanates and N-alkyl azomethines was found to proceed easily without catalyst, particularly in refluxing chlorobenzene. The physical and chemical properties, including n.m.r. spectra of the oily triazinones, are contrasted with the newly discovered solid adducts arising from low temperature reaction of azomethine and chlorophenyl isocyanates. From stoichiometry of the reaction, elemental analysis, molecular weight of the products, and spectral analyses, the new materials (II) were found to incorporate two isocyanate and three azomethine moieties in their molecular make-up. The relative merits are considered for assigning II a molecular structure arising from a complex between a four and six-membered ring (III, IV) versus a ten-membered ring system (V, VI, VIa).     

A fully computer controlled, low cost STM

Summary If one examines the components of a scanning tunneling microscopy system, one finds, that for a great part the computer determines the abilities of it. Once a stable mechanical setup is constructed, it depends on the control part, which features the whole system shows and how convenient one can work with it. Here we present a scanning tunneling microscope which is, as far as possible, computer controlled and can be fully operated from a user surface on the computer. This has been achieved by the use of a two computer concept. The mechanics, electronics and software were self-developed; all other components were selected under the aspect of costs resulting in a low priced and yet high performance system.     

Quantum oscillations in the seebeck-effect of mercury selenide in high magnetic fields

Quantum oscillations in the thermoelectric power of annealed HgSe-crystals were investigated between 20 and 80 K in transverse magnetic fields up to 10 T. It was possible to describe the data quantitatively by using Obraztsov's formula and taking account of the collision damping by introducing a Dingle factor.     

Impurity conduction and magnetoresistance in lightly dopedn-type GaAs

Measurements of the resistivity and magnetoresistance of epitaxially grownn-type GaAs (N _D ~ 1–2 × 10¹⁵ cm^–3) at 4.2 K and below are reported. The hopping resistivity ( \fractal⁴ N_D )\left( {\frac{{ta}}{{\lambda ^4 N_D }}} \right) ,t having a value of 0.06 in disagreement with a recent theoretical calculation oft=0.04. In the high magnetic field region above 3T the data are described by exp [q ( ² a _B N _D)^–1/2], where is the characteristic magnetic length anda _B is the magnetic field dependent Bohr radius. From the experiments a value ofq=0.68 is deduced, while the theory predictsq=0.98.     

Effects of growth conditions on the surface structure of CdTe studied by a scanning tunneling microscope

Summary CdTe buffer layers are widely used as substrate materials for the molecular beam epitaxial (MBE) growth of Hg_1–x Cd _x Te because of the small lattice mismatch. With the help of a scanning tunneling microscope (STM) and a scanning electron microscope (SEM) the surface topographies of epitaxial CdTe layers grown under different conditions were studied quantitatively. It was found that photoassistance during growth enhances the formation of pyramidal hills with a typical height of 1000 . The use of an excess of Cd completely changes the surface morphology towards 2-dimensional growth and the remaining layer roughness was less than 50 . These initial results suggest that the Cd rich conditions provide a promising method for the growth of large, flat layers.