Explosive crystallization of amorphous germanium

Abstract

We have obtained experimental confirmation of the prediction that explosive crystallization of amorphous germanium proceeds via an intermediate melting step.

Surface undulations in explosive crystallization: A nonlinear analysis of a thermal instability

“…In explosive crystallization in Ge, the a phase probably melts first before crystallizing [32,22,15]. Whether the same happens in Sb is not clear, but experiments on Yb and Bi [30] at liquid He temperatures seem to rule out the presence of a liquid zone in these materials.…”

“…In our analysis, we have not taken the possible existence of such a liquid zone into account. However, since these liquid regions are probably much smaller than the wavelength of the undulations [32,22,15], we believe their presence would not modify the thermal instability qualitatively.…”

“…The straight front will now be unstable and break up into protrusions with a typical length determined by a capillary length and the thermal length x/V~s (the slope of the temperature in front of the boundary). The observation by Leamy et al [22] that the surface of explosively crystallized Ge layers showed undulations that "are composed of froth-like bubbles that are aligned in irregular rows" [22] may be related to such effects.…”

“…Under favorable experimental conditions, layers of amorphous Sb [3][4][5][6][7][8], Ge [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], Si [24][25][26][27][28] and other materials [29,30] can crystallize very rapidly when crystallization is initiated by a laser pulse or by impact with a stylus. The name explosive crystallization stems from the fact that the speed of the crystallization front can be of the order of meters per second.…”

In situ investigation of explosive crystallization in a-Ge: Experimental determination of the interface response function using dynamic transmission electron microscopy

“…24 Additionally, indirect evidence has been obtained using transient conductance and timeresolved reflectivity measurements in Si, 23 as well as the redistribution of dopant impurities in Ge (i.e., by assuming the material at the interface has diffusion characteristics of l-Ge). 25 Gibbs free energy calculations suggest that this liquid is metastable in the temperature range T ma < T < T mc , 26 since the crystalline phase has the lowest free energy over this range. The appearance of a transient liquid-like phase in this temperature range is due to the rapid rate of the a-l transition compared to the direct a-c transformation.…”