Structure of crystallized particles in sputter-deposited amorphous germanium films

Abstract

Pristine thin films of amorphous Ge prepared by sputtering are unstable and form coarse crystalline particles of 100 nm in size upon crystallization by electron irradiation. These crystalline particles exhibit unusual diffraction patterns that cannot be understood from the diamond cubic structure. The structure has previously been assumed to be a metastable hexagonal form. In the present work, the structure of the coarse crystalline particles has been analysed in detail by transmission electron microscopy, considering the possibility that those diffraction patterns might occur with the diamond cubic structure if the particle consists of thin twin layers. By high-resolution lattice imaging the particles have been shown to be of the diamond cubic structure containing a high density of twins and stacking faults parallel to {111}. With such defects, diffraction patterns can be complex because of the following effects: superposition of two or more diffraction patterns of the same structure but of different orientations, double diffraction through twin crystals, and streaks parallel to the thin crystal which give rise to extra diffraction spots. It is found that diffraction patterns taken from various orientations can be explained in terms of these effects.

Effects of hydrogen on structure and crystallization behavior of sputter-deposited amorphous germanium films

“…3(g) for a-Ge aged for 7 months. In our previous study, 12) we analyzed the high-resolution TEM image and the diffraction patterns of a single CP to conclude that the forbidden reflection at (222) is due to twins and stacking faults parallel to {111}, which are an intrinsic property of CPs. The forbidden reflection at (222) appeared in the CPs of the a-Ge:H aged for 3-5 d (a) and 5 months (b).…”

“…11) Then, we found that defective structures are characteristic of CPs: a number of planar defects parallel to {111} form during crystallization. 12) Most recently, the formation of planar defects is attributed to the rapid formation of CPs, so-called explosive crystallization, which occurs in not stabilized films but pristine films. 13) These are unique properties of sputter-deposited pure a-Ge we have found up to now.…”

“…The partial pressure of Ar was fixed to be 0.7 Pa according to a series of our previous studies. [10][11][12][13] The partial pressure of H 2 was set between 0 and 0.55 Pa by referring to a report by Heya et al, 20) who prepared amorphous Si films with various hydrogen concentration by sputtering under the conditions of several ratios of H 2 and Ar pressures.…”

The relation between amorphous structure and explosive crystallization of sputter-deposited amorphous germanium thin films

“…5) While the fine nanograins were of the diamond cubic structure, the coarse particles exhibited unusual diffraction patterns that cannot be understood from the diamond cubic structure, and had been assumed to be a metastable hexagonal form. 5) In yet another paper, 6) we reported that the structure of the crystalline particles was not hexagonal but cubic, and a number of planar defects parallel to {111} were included. These papers [3][4][5][6] are hereafter referred to as papers I-IV.…”

“…5) In yet another paper, 6) we reported that the structure of the crystalline particles was not hexagonal but cubic, and a number of planar defects parallel to {111} were included. These papers [3][4][5][6] are hereafter referred to as papers I-IV.…”