Shubha Gokhale

Photoemission and x-ray diffraction study of the Er/Si(111) interface

The Er-Si interface has been studied using XPS, UPS and glancing incidence XRD. Room temperature investigations of the evolving Er-Si interface reveal a two step reaction. Initially reacted clusters of silicon rich silicide form. At higher coverages, metal rich Er5Si3 formation takes place. High temperature annealing leads to stable disilicide formation at the interface.

XPS and XRD investigations of Dy/Si interface

The interaction of dysprosium metal atoms with silicon (111) surface at different temperatures has been investigated using X-ray photoelectron spectroscopy and X-ray diffraction analysis. Si 2p and Dy 3d52 spectral lines are used to propose the DySi interaction in the interface region. Even at room temperature (300 K) strong interaction between Dy and Si atoms takes place due to charge transfer from Dy to Si. At this temperature, at the interface, a predominantly Dy-rich Dy5Si3 phase is observed. Whereas at an annealing temperature of 623 K a silicon-rich DySi2 − x phase is observed. At an intermediate temperature of 423 K both these phases are seen with some amorphous background.

Chemical interaction at the Tm/Si(111) interface

Abstract Interface investigations of Tm/Si(111) have been carried out using XPS, UPS and glancing incidence XRD at various temperatures. Room temperature interface evolution takes place in three stages. Initially there is no reaction between adsorbate and substrate and Tm clusters are formed. In the second regime cluster coalescence takes place and there is a strong interaction between Tm and Si to form TmSi 2 . Finally, metal-rich Tm 5 Si 3 phase formation takes place. High-temperature studies reveal that at 473 K, predominantly the Tm 5 Si 3 phase is present with some TmSi 2 , while the film is completely converted into a disilicide phase by annealing at 673 K. Binding energies of Si 2p corresponding to various Tm silicides are identified. At all temperatures, throughout the interface development, Tm was found to be trivalent in nature.

Chemical reactivity and band offset at the CdS/Si interface

Transport phenomena at heterojunctions are critically governed by chemical reactivity and the valence-band offset at the interface. Here we report our investigations carried out on the CdS/Si(111) interface using X-ray and ultraviolet photoelectron spectroscopy and glancing-incidence X-ray diffraction. Weak reactivity between CdS and Si(111) has been observed. A partial charge transfer interaction is suggested to explain the weak reactivity at the interface on the basis of the electronegativity difference. Hexagonal phase of CdS is preferentially grown at 700 K. The valence-band offsets obtained for the interfaces grown at 300 and 700 K are 1.6 and 1.3 eV, respectively. The effects of chemical reactivity and disorder are discussed.