The influence of lattice oxygen on the initial growth behavior of heteroepitaxial Ge layers on single crystalline PrO2(111)∕Si(111) support systems

Abstract

A combined structure and stoichiometry study on the growth behavior of single crystalline Ge(111) layers on PrO2(111)∕Si(111) heterostructures is presented. Ex situ x-ray diffraction techniques indicate that the interaction between Ge and PrO2(111) results in a complete reduction of the buffer oxide to a cubic Pr2O3(111) film structure. In situ reflection high energy electron diffraction, x-ray and ultraviolet photoelectron spectroscopy studies demonstrate that this chemical reduction of the oxide support occurs during the initial Ge growth stage. The interaction of PrO2 with Ge results in the formation of an amorphous Ge oxide layer by the diffusion of lattice oxygen from the dielectric to the forming semiconductor deposit. After the complete conversion of PrO2 to cubic Pr2O3, the supply of reactive lattice oxygen is exhausted and the continuous Ge deposition reduces the initially formed amorphous GeO2-like film to GeO. The sublimation of volatile GeO uncovers the single crystalline cubic Pr2O3(111) film surface which provides a thermodynamically stable template for elemental Ge heteroepitaxy. A Volmer–Weber growth mode is observed which results after island coalescence in the formation of atomically smooth, single crystalline Ge(111) layers.

Photoemission study of praseodymia in its highest oxidation state: The necessity of in situ plasma treatment

“…[10][11][12][13][14] Spectrum (a) in Fig. 3 shows a typical Pr 3d spectrum of an ex situ prepared PrO 2 layer on Si(111) that we obtained in our own experiments.…”

Structure of oxygen-plasma-treated ultrathin praseodymia films on Si(111)

“…4,5 For this purpose hex-Pr 2 O 3 films are usually exposed to molecular oxygen at high pressure, but full transformation to PrO 2 (111) has not been achieved yet.…”

Epitaxy of single crystalline PrO2 films on Si(111)

“…3 In the latter field, especially heteroepitaxial rare earth oxide thin films on silicon attract increasing research interest. For example, single crystalline oxides on silicon systems are discussed as highly functional buffer oxide structures to achieve the global integration of alternative semiconductors on Si ͓engineered silicon wafers, e.g., Ge/ PrO 2 , 4 InP/ Gd 2 O 3 5 ͔. Another key technology is the local integration of epitaxial rare earth oxides on Si to improve the performance of future Si device technologies ͑e.g., high-k oxides for complementary metal oxide semiconductor applications͒.…”