Preparation and properties of thin polycrystalline MnSi1.73 films

Thin MnSi1.73 films were prepared by a DC sputter method in a high vacuum deposition chamber. As target material a MnSi2 silicide target was used. Films were deposited onto quartz substrates at different temperatures (330-875 K) without any annealing steps after the sputter process. The composition of the samples was determined by Rutherford backscattering spectroscopy. Within the detection limit of this method no contamination in the films was found. The crystalline structure of the films was analyzed by transmission electron microscopy. At substrate temperatures of 530 K always a tetragonal crystalline phase of MnSi1.73 was observed. The specific resistivity and the Hall mobility of the samples were determined in the temperature range from 300 to 25 K. The results of the electrical measurements verify the low crystallization temperature of the films. The character of the electrical transport in the crystalline films is strongly influenced by the preparation temperature. With rising substrate temperature the sign of the temperature coefficient of resistivity at room temperature changes from negative to positive values. At room temperature Hall mobilities in the region of 1.4 cm(2) V-1 s(-1) were obtained. The temperature dependence of the electrical transport properties can be interpreted in the picture of a degenerated semiconductor. With optical measurements at room temperature an indirect gap of 0.46 eV was determined. The structure of the transmission spectra was influenced by the different heat treatments in the sample preparation.