Impact of nanosecond UV laser pulses on the surface of germanium single crystals

For the first time, a detailed comprehensive study of the "dry" etching of dislocation and dislocation-free germanium samples on the {111}, {110} and {100} planes has been carried out. Etching was carried out by exposure to pulses of nanosecond UV laser radiation of subthreshold intensity (wavelength 355 nm, duration ~ 10 ns, energy density ~ 0.5–1.3 J/cm², pulse repetition rate 100 Hz, divergence 1–2 mrad). Before and after laser heat treatment of the surface, the samples were examined using a Zygo optical profilometer and a scanning electron microscope. Features of the nature of damage to surfaces corresponding to different crystallographic planes of single crystals of industrial dislocation germanium are revealed. They are compared with data on subthreshold damages of typical dislocation-free crystals.

It is shown that in dislocation samples of germanium on the {111} plane, it is possible to create a regime of exposure to radiation, leading to the formation of etch pits that are outwardly identical to dislocation pits detected during selective chemical etching. Their concentration corresponds in order of magnitude to the density of dislocations.

On the {100} plane of dislocation samples, etching results were also found, which clearly have a crystallographic nature. At an energy density of the acting radiation ≥ 0.4 J/cm², on the surfaces of dislocation ({100} plane) and dislocation-free germanium ({111}, {100}, {110} planes), only individual spots ~ 50 μm in size were registered, as well as individual microcraters ~ 0.1–1 μm in size, which do not have crystallographic features. The possibility of environmentally friendly detection of dislocations in germanium without the use of chemical reagents is shown.

1. Libenson M.N., Yakovlev E.B., Shandybina G.D. Interaction of laser radiation with matter (power optics). Part 1. Absorption of laser radiation in matter [Veiko V.P., ed.]. St. Petersburg: ITMO; 2008. 141 p. (In Russ.)

2. Zheleznov V.Yu., Malinskiy T.V., Mikolutskiy S.I., Rogalin V.E., Filin S.A., Khomich Yu.V., Yamshchikov V.A., Kaplunov I.A., Ivanova A.I. Laser etching of Germanium. Technical Physics Letters. 2021; 47(10): 734—736. https://doi.org/10.1134/S1063785021070282

3. Malinskiy T.V., Rogalin V.E. Prethreshold effects, when copper and its alloys were impacted to ultraviolet laser pulses. Technical Physics. 2022; 92;(2): 211—215. https://doi.org/10.21883/TP.2022.02.52950.225-21 4. Murzin S.P., Balyakin V.B., Gachot C., Fomchenkov S.A., Blokhin M.V., Kazanskiy N.L. Ultraviolet nanosecond laser treatment to reduce the friction coefficient of silicon carbide ceramics. Applied Sciences. 2021; 11(24): 11906. https://doi.org/10.3390/app112411906

4. Khomich V.Y., Shmakov V.A. Mechanisms of direct laser nanostructuring of materials. Physics-Uspekhi. 2015; 58(5): 455—465. https://doi.org/10.3367/UFNe.0185.201505c.0489

5. Khomich V.Yu., Shmakov V.A. Formation of periodic nanodimensional structures on the surface of solids during phase and structural transformations. Doklady Physics. 2012; 57(9): 349—351.

6. Bronnikov K.A. Formation of laser-induced periodic surface structures on films of metals and semiconductors. Diss. Cand. Sci. (Phys.-Mat.). Novosibirsk; 2022. 106 p. (In Russ.)

7. Iqbal M.H., Bashir S., Rafique M.S., Dawood A., Akram M., Mahmood K., Hayat A., Ahmad R., Hussain T., Mahmood A. Pulsed laser ablation of germanium under vacuum and hydrogen environments at various fluences. Applied Surface Science. 2015; 344: 146—158. https://doi.org/10.1016/j.apsusc.2015.03.117

8. Manoj K., Mavi H.S., Rath S., Shukla A.K., Vankar V.D. Fabrication of nanopatterned germanium surface by laser-induced etching: AFM, Raman and PL studies. Physica E: Low-dimensional Systems and Nanostructures. 2008; 40(9): 2904—2910. https://doi.org/10.1016/j.physe.2008.02.007

9. Chumakov A.N., Luchkouski V.V., Nikonchuk I.S., Matsukovich A.S. Silicon ablation in air by mono- and bichromatic laser pulses with wavelength 355 and 532 nm. Technical Physics. 2022; 92(1): 16—24. https://doi.org/10.21883/TP.2022.01.52527.202-21

10. Bosi M., Atolini G. Germanium: Epitaxy and its application. Progress in Crystal Growth and Characterization of Materials. 2010; 56(3-4): 146—174. https://doi.org/10.1016/j.pcrysgrow.2010.09.002

11. Kaplunov I.A., Rogalin V.E. Optical properties and application of germanium in photonics. Photonics Russia. 2019; 13(1): 88—106. https://doi.org/10.22184/FRos.2019.13.1.88.106

12. Korotaev V.V., Mel'nikov G.S., Mikheev S.V., Samkov V.M., Soldatov Yu.I. Fundamentals of thermal imaging. St. Petersburg: ITMO; 2012. 122 p. (In Russ.)

13. Shimanskii A.F., Gorodishcheva A.N., Kopytkova S.A., Kulakovskaya T.V. Thermal stability of the properties of germanium crystals for IR optics. Journal of Physics: Conference Series. 2019; 1353(1): 12062. https://doi.org/10.1088/1742-6596/1353/1/012062

14. Mashanovich G.Z., Mitchell C.J., Penades J.S., Ali Z., Khokhar A.Z., Littlejohns C.G., Cao W., Qu Zh., Stanković S., Gardes F.Y., Masaud T.B., Chong H.M., Mittal V., Murugan G.S., James S., Wilkinson J.S., Peacock A.C., Nedeljkovic M. Germanium mid-infrared photonic devices. Journal of Lightwave Technology. 2017; 35(4): 624—630. https://doi.org/10.1109/JLT.2016.2632301

15. Molchanov V.Ya., Kitaev Yu.I., Kolesnikov A.I., Narver V.N., Rozenshtein A.Z., Solodovnikov N.P., Shapovalenko K.G. Theory and practice of modern acousto-optics. Moscow: MISiS; 2015. 459 p. (In Russ.)

16. Ordu M., Guo J., Pack G. Ng, Shah P., Ramachandran S., Hong M.K., Ziegler L.D., Basu S.N., Erramilli S. Nonlinear optics in germanium mid-infrared fiber material: Detuning oscillations in femtosecond mid-infrared spectroscopy. AIP Advances. 2017; 7(9): 095125. https://doi.org/10.1063/1.5003027

17. Depuydt B., Theuwis A., Romandic I. Germanium: From the first application of Czochralski crystal growth to large diameter dislocation-free wafers. Materials Science in Semiconductor Processing. 2006; 9(4-5): 437—443. https://doi.org/10.1016/j.mssp.2006.08.002

18. Claeys L., Simoen E., eds. Germanium-based technologies: from materials to devices. 1st ed. Berlin: Elsevier; 2007. 480 p. https://doi.org/10.1016/S1369-7021(07)70279-1

19. Malinskiy T.V., Zheleznov V.Yu., Rogalin V.E., Kaplunov I.A. Experimental study of the influence of laser radiation power on the reflection coefficient of germanium and silicon at a wavelength of 355 nm. Journal of Physics Conference Series. 2021; 2103(1): 012154. https://doi.org/10.1088/1742-6596/2103/1/012154

20. Bublik V.T., Dubrovina A.N. Methods of studying the structure of semiconductors and metals. Moscow: Metallurgiya; 1978. 272 p. (In Russ.)

21. Voronov V.V., Dolgaev S.I., Lavrishchev S.V., Lyalin A.A., Simakin A.V., Shafeev G.A. Formation of conic microstructures upon pulsed laser evaporation of solids. Quantum Electronics. 2000; 30(8): 710—714. https://doi.org/10.1070/QE2000v030n08ABEH001795

22. Gonov S.Zh. Features of the impact of milli- and nanosecond laser radiation on semiconductor materials of solid-state electronics. Diss. Cand. Sci. (Eng.). Nalchik; 2007. 130 p. (In Russ.)

23. Veiko V.P., Dorofeev I.A., Imas Ya.A., Kalugina T.I., Libenson M.N., Shandybina G.D. Formation of periodic structures on a silicon surface under the effect of millisecond duration pulse deodymium lasers. Pisma v zhurnal tekhnicheskoi fiziki. 1984; 10(1): 15—20.

24. Ivlev G.D., Malevich V.L. Heating and melting of single-crystal germanium by nanosecond laser pulses. Soviet Journal of Quantum Electronics. 1988; 18(12): 1626—1627. https://doi.org/10.1070/QE1988v018n12ABEH012781

25. Ehrhardt M., Lorenz P., Bauer J., Heinke R., Hossain M.A., Han B., Zimmer K. Dry etching of germanium with laser induced reactive micro plasma. Lasers in Manufacturing and Materials Processing. 2021; 8(3): 237—255. https://doi.org/10.1007/s40516-021-00147-1

26. Poate J.M., Foti G., Jacobson D.C., eds. Surface modification and alloying by laser, ion and electrn beams. NY: London: Plenum Press; 1983. 424 p. (Russ. Transl.: Poate J.M., Foti G., Jacobson D.C., eds. Modifitsirovanie i legirovanie poverkhnosti lazernymi, ionnymi i elektronnymi puchkami. NY: London: Plenum Press; 1983. 424 p.)

27. Ashikkalieva K.H., Kanygina O.N. Formation of periodic structures on the surface of single-crystal silicon under pulsed laser action. Deformaciya i razrushenie materialov. 2012; (5): 12—15. (In Russ.)

28. Okatov M.A., Antonov E.A., Baigozhin A. Handbook of the optical technologist. St. Petersburg: Politekhnika; 2004. 679 p. (In Russ.)

29. Mikolutskiy S.I., Khasaya R.R., Khomich Yu.V., Yamshchikov V.A. Formation of various types of nanostructures on germanium surface by nanosecond laser pulses. Journal of Physics Conference Series. 2018; 987: 012007. https://doi.org/10.1088/1742-6596/987/1/012007

30. Anisimov S.I., Imas Ya.A., Romanov G.S., Khodyko Yu.V. The effect of high-power radiation on metals. Moscow: Nauka; 1970. 272 p. (In Russ.)

31. Zheleznov V.Yu., Malinskiy T.V., Mikolutskiy S.I., Rogalin V.E., Filin S.A., Khomich Yu.V., Yamshchikov V.A., Kaplunov I.A., Ivanova A.I. Modification of germanium surface exposed to radiation of a nanosecond ultraviolet laser. Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering. 2020; 23(3): 203—212. (In Russ.). https://doi.org/10.17073/1609-3577-2020-3-203-212

32. Konov V.I., Prokhorov A.M., Sichugov V.A., Tischenko A.V., Tokarev V.N. Time and space evolution of the periodic structures induced onto the surface of laser-irradiated solid samples. Zhurnal tekhnicheskoj fiziki; 1983; 53(12): 2238—2242. (In Russ.)

33. Kaplunov I.A., Kolesnikov A.I., Ivanova A.I., Podkopaev O.I., Tretiakov S.A., Grechishkin R.M. Surface micromorphology of germanium single crystal boules grown from melt. Journal of Surface Investigation. X-Ray, Synchrotron and Neutron Techniques. 2015; 9(3): 630—635. https://doi.org/10.1134/S102745101503026X

34. Gadiyak G.V., Karpushin A.A., Kushkova A.S., Morokov Yu.N., Repinsky S.M., Shklyaev A.A. Wulf diagram for silicon and germanium surfaces. Quantum-chemical calculation. Poverkhnost'. Fizika, khimiya, mekhanika. 1988; (3): 23—28. (In Russ.)