Nucleation-controlled gold-induced-crystallization for selective formation of Ge(100) and (111) on insulator at low-temperature (∼250 °C)

Abstract

Selective formation of Ge(100) and (111) on amorphous-insulator at low-temperatures (∼250 °C) is realized through gold-induced-crystallization using a-Ge/Au/SiO2 stacked-structures by combining interface-energy-modulation of substrates. Introduction of thin-Al2O3 layers (∼7 nm thickness) at a-Ge/Au interfaces enables large-grain (≥20 μm) Ge(111) formation, which is speculated to be due to suppression of random bulk-nucleation and domination of (111)-oriented interface-nucleation on SiO2. To examine this speculation, Al2O3-covered substrates are employed. This results in formation of Ge(100), due to energetically favorable (100)-oriented interface-nucleation on Al2O3. Consequently, large-grain (≥20 μm) Ge(100) and (111) are achieved on amorphous-insulators at 250 °C. This technique is very useful to realize flexible-electronics.

Growth and applications of GeSn-related group-IV semiconductor materials

“…Research groups at Kyushu University and Tsukuba University have individually studied the eutectic-metal induced crystallization of Si [55], Ge [56,57], and Si 1−x Ge x [58,59], aiming for orientation control. From a technological point of views, Park et al [60] and Toko et al [61] individually demonstrated the sub-200°C formation of highly (111)-oriented poly-Ge films on flexible plastic substrates.…”

Influence of order degree of amorphous germanium on metal induced crystallization

“…Located at 27.51, the peak had a FWHM value of only 0.161. This single (111) orientation was explained from the view point of the interfacial energy minimization between the Ge layer and the SiO 2 substrate [22][23][24]. The crystal seed originating from pre-annealing had a different orientation compared to crystal grains induced by the MIC process, causing a conflict that slowed mutual diffusion between Al and Ge.…”

The Larger Grain and (111)-Orientation Planes of Poly-Ge Thin Film Grown on SiO<sub>2</sub> Substrate by Al-Induced Crystallization

“…All thin films have a sharp peak around 13.7˚ indicating preferential (111)-orientation planes. The (111)-orientation planes are interpreted from the viewpoint of the minimal interfacial energy between Ge thin film and SiO 2 substrate [21]. The FWHM values of the sharp peak of XRD rocking curve are plotted in the insert figure, which indicates that the lower annealing temperature provides weaker (111)-orientation planes but larger FWHM values.…”