Pulsed modification of germanium films on silicon, sapphire, and quartz substrates: Structure and optical properties

The structural and optical properties of thin Ge films deposited onto semiconducting and insulating substrates and modified by pulsed laser radiation are studied. The films are deposited by the sputtering of a Ge target with a low-energy Xe$^+$ ion beam. Crystallization of the films is conducted by their exposure to nanosecond ruby laser radiation pulses ($\lambda$ = 0.694 $\mu$m) with the energy density $W$ = 0.2–1.4 J cm$^{-2}$. During pulsed laser treatment, the irradiated area is probed with quasi-cw (quasi-continuous-wave) laser radiation ($\lambda$ = 0.532 and 1.064 $\mu$m), with the reflectance recorded $R(t)$. Experimental data on the lifetime of the Ge melt are compared with the results of calculation, and good agreement between them is demonstrated. Through the use of a number of techniques, the dependences of the composition of the films, their crystal structure, the level of strains, and the reflectance and transmittance on the conditions of deposition and annealing are established.