Time-Resolved TEM of Transient Effects in Pulse Annealing of Ge and Ge–Te Films

Abstract

An improved version of time‐resolved TEM is described which detects electron pulse‐induced phase transitions with a resolution of 3 ns in specimen areas above 0.3 μm Ø. The heating pulse automatically is switched off within 15 ns after the phase transition is detected. Using a train of needle pulses the specimen also may be probed outside or after the heating pulse. The method is applied to pulse annealing of amorphous Ge and Ge0.6Te0.4 films by electron beams depositing ≈ 1 kW/cm2. Formation times of crystals are determined (5 to 10 ns) and fast disintegration and recrystallization is traced. Pronounced thermal aftereffects are observed, triggering even crystallization within several μs after the end of the heating period.

In situ dynamic transmission electron microscopy characterization of liquid-mediated crystallization of amorphous Ge

“…Rapid crystallization of amorphous semiconductor film mediated by a very highlyundercooled, transient liquid layer has been called "explosive" crystallization 12 because it may generate visible light and considerable heat. 13,14 Explosive crystallization has been studied in Si, [15][16][17][18] Ge, [4][5][6][7][8][9]12,14,16,[19][20][21][22][23][24][25][26] and Sb. 13,[27][28][29] There is also evidence that Sb-rich alloys such as GeSb 6 Te may undergo rapid liquid-mediated growth.…”

“…Transmission electron microscopy (TEM) has been used for in situ studies of laser-and electron-beam-induced crystallization of amorphous Ge. 7,8,16,21,22,25,26,32,33 In these studies, a minute area of an electron transparent specimen of amorphous Ge is heated with a focused laser or electron beam, resulting in high local temperature gradients. A region of an electron transparent sample may be heated with a pulsed laser in nanoseconds and the crystallization of the heated region takes on the order of 1 s, but it takes much longer for the temperature profile to homogenize, because the heat flow out is mainly through the plane of the electron transparent thin film (radiative cooling is insignificant on these timescales).…”