Nanoobjects microscopy

Layer polymorphous crystallizations of amorphous films: structural and kinetic aspects
Bagmut A.G., Bagmut I.A.
Department of Physics of the National Technical University “Kharkiv Polytechnic Institute” of Ukraine. NTU “KhPI” 2, Kyrpychova str., 61002, Kharkiv, Ukraine.
E-mail: agbagmut@gmail.com

Structural and geometric aspects of layer polymorphic crystallization of thin amorphous films were considered. The review of electron microscopic studies of crystallization “in situ” of amorphous films under the influence of the electron beam was provided [1]. Digital video recording of structural and phase changes, occurring in the film, was applied. Kinetic crystallization curves were constructed and the parameters reflecting the growth of crystals of various morphologies in amorphous film were defined.

Fig.1. Growth of crystals in amorphous films: disk-shaped crystal of V2O3 (a), sickle-shaped crystal of Cr2O3 (b) and ring-shaped crystal of Cr2O3 (c).

a

R

0.68 μm

φ

R

vτ

vn

b

0.5 μm

c

1.7 μm

In the case of laser sputtering of metal targets (Cr, V) in an oxygen atmosphere, amorphous films are formed on substrates at a room temperature. Electron-beam crystallization of amorphous films is accompanied by the formation of Cr2O3 and V2O3 crystals of three basic morphological forms (Fig. 1): disk-shaped, sickle-shaped and needle-shaped, the kinetics of growth of which is different. At a fixed electron current density through the sample, the growth of disk-shaped crystals occurs at a constant rate; the degree of crystallinity is x ~ t2, and the rate of change in the fraction of the crystalline phase x't ~ t. Sickle-shaped (at the initial stage) crystal, as it grows, changes its morphology in the sequence: sickle-shaped → ring-shaped → disk-shaped crystal.

1. Bagmut A. G., Bagmut I. A. Modes and kinetics of crystals growth in amorphous films of oxides // Molecular Crystals and Liquid Crystals.- 2018.- 673, P. 120-124.