S. Vaidehi

Bio: S. Vaidehi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Band gap & Thin film. The author has an hindex of 1, co-authored 2 publications receiving 4 citations.

Variation of energy gap and resistivity minimum position with thickness in bismuth thin films

Abstract: Bismuth thin films of different thicknesses between about 20 and 225 nm are vacuum deposited at room temperature in a vacuum of 3 × 10−3 Pa. The films are heat-treated “in situ” and the resistances monitored. It is found that the resistivity-temperature plots of the films after heat-treatment are non-linear and exhibit a minimum whose position is a function of thickness. It is also found that the films behave as semiconductors, the band gap decreasing with increasing thickness. The observations are interpreted on the basis of quantum size effect and the limitation of the electronic mean free path by the grain size of the films. Dunne Wismuth-Schichten verschiedener Dicken zwischen 20 und 225 nm werden bei Zimmer-temperatur im Vakuum von 3 × 10−3 Pa hergestellt. Die Schichten werden “in situ” getempert und der Widerstand verfolgt. Es wird gefunden, das die Widerstands-Temperatur-Verlaufe der Schichten nach der Warmebehandlung nichtlinear sind und ein Minimum aufweisen, dessen Lage von der Schichtdicke abhangt. Es wird ebenfalls gefunden, das sich die Schichten wie Halbleiter verhalten, wobei die Bandlucke mit zunehmender Schichtdicke abnimmt. Die Beobachtungen werden auf der Grundlage des Quantensize-Effekts und der Begrenzung der mittleren freien Weglange der Elektronen durch die Korngrose der Schichten erklart.

Semiconducting behaviour of thin bismuth films vacuum-deposited at different substrate temperatures

Abstract: Thin bismuth films (thickness 25 nm) have been vacuum-deposited onto glass substrates at different substrate temperatures in a vacuum of 2×10−5 torr. The resistance of the films has been measured as a function of temperaturein situ during and after annealing. It is found that the resistance of all the annealed films decreases with increasing temperature thus showing a semiconducting type of behaviour. The films do not show a resistivity minimum observed in thicker films [1]. The absence of a resistivity minimum is attributed to the thinness of the films and consequent larger energy band gap and smaller grain size.

Semiconducting behavior of Ag2Te thin films and the dependence of band gap on thickness

Abstract: Thin films of Ag2Te of various thicknesses in the range 500–1500 A have been prepared by thermal evaporation of the compound under vacuum on clean glass substrates held at room temperature. The electrical resistance of the films has been measured as a function of temperature during heating, which was carried out immediately after the film formation. The observed exponential decrease of resistance with temperature up to the transition point points to the semiconducting nature of the low temperature polymorph of Ag2Te. The band gap of the low temperature phase is calculated for various thicknesses of the films and it is found that the band gap is a function of film thickness, increasing with decreasing thickness. The increase in the band gap, which was found to be inversely proportional to the square of the film thickness, is attributed to quantization of electron momentum component normal to film plane.

Thickness dependence of electrical resistivity and activation energy in AgSbTe2 thin films

Abstract: Thin films of AgSbTe2 with different thicknesses were prepared by thermal evaporation on glass substrates held at room temperature. The films were all found to be semiconducting in nature. The film resistivity was found to be a function of inverse thickness and was discussed on the basis of the effective mean free path model. The activation energy was found to be a linear function of the inverse square of film thickness. It was attributed to the quantization of the momentum component of charge carriers normal to the film plane.

Semiconducting behaviour of thin bismuth films vacuum-deposited at different substrate temperatures

Abstract: Thin bismuth films (thickness 25 nm) have been vacuum-deposited onto glass substrates at different substrate temperatures in a vacuum of 2×10−5 torr. The resistance of the films has been measured as a function of temperaturein situ during and after annealing. It is found that the resistance of all the annealed films decreases with increasing temperature thus showing a semiconducting type of behaviour. The films do not show a resistivity minimum observed in thicker films [1]. The absence of a resistivity minimum is attributed to the thinness of the films and consequent larger energy band gap and smaller grain size.

Effect of Thermal Annealing on the Characteristics of Bi-Sb Thin Film Structure

Abstract: In this study, Bi-Sb thin film structure was prepared by thermal evaporation method. The electrical, optical transmission and structural characteristics of the prepared samples were introduced before and after thermal annealing process. At temperature of 500 °C, the absorption of the structure was improved to reach 97% at near-infrared region. As well, the thermal annealing caused to reduce the bulk resistance of the Bi-Sb thin film structure. The mor-phology of Bi-Sb structure was also improved by thermal annealing as characteristic islands of the structure appear clearly in form hexagonal areas distinct from each other. This study is aiming to examine such structures if they are employed as photonic devices such as photodetectors, LED’s and optical switches.