In this work, the structural transformations of a suboxide vacuum-deposited film of SiO_1.3 composition annealed in an inert atmosphere in a wide temperature range of 100 °C–1100 °C were characterized by the reflection-transmission spectroscopy technique. The experimental spectroscopic data were used to obtain the spectra of the absorption coefficient α(hν) in the absorption edge region of the film. Based on their processing, the dependences of Urbach energy E_U and optical (Tauc) bandgap E_o on the annealing temperature were obtained. An assessment of the electronic band gap (mobility gap) E_g was also carried out. Analysis of these dependences allowed us to trace dynamics of thermally stimulated disproportionation of the suboxide film and the features of the formation of nanocomposites consisting of amorphous and/or crystalline silicon nanoparticles in an oxide matrix.

1.

1.         Savage JA. Infrared Optical Materials and their Antireflection Coatings. Bristol: Adam Higler Ltd; 1985.

2.

2.         Wetch KW. Large-range refractive-index control of silicon monoxide antireflection coatings using oblique incident thermal evaporation. Applied Optics. 1991; 30(28): 4133. doi: 10.1364/ao.30.004133

3.

3.         Tomozeiu N. Silicon Oxide (SiO_x, 0< x < 2): a Challenging Material for Optoelectronics. In: Predeep P (editor). Optoelectronics: Materials and Techniques. IntechOpen; 2011. pp. 55–98.

4.

4.         Melnik VP, Popov VG, Romanyuk BM, et al. Luminescent properties of the structures with embedded silicon nanoclusters: Influence of technology, doping and annealing (Review). Semiconductor Physics, Quantum Electronics & Optoelectronics. 2023; 26(3): 278–302. doi: 10.15407/spqeo26.03.278

5.

5.         Falcony C, Estrada-Wiese D, De Anda J, et al. Low temperature (<700 °C) SiO₂ and Si-rich SiO₂ films: Short review. Journal of Vacuum Science & Technology B. 2023; 41(3). doi: 10.1116/6.0002531

6.

6.         Sopinskyy MV, Vlasenko, NA, Lisovskyy IP, et al. Formation of nanocomposites by oxidizing annealing of SiO _x and SiO _x <Er,F> films: Ellipsometry and FTIR analysis. Nanoscale Research Letters. 2015; 10(1). doi: 10.1186/s11671-015-0933-0

7.

7.         Michailovska K, Indutnyi I, Shepeliavyi P, et al. The effect of fluorine–hydrogen treatment on the photoluminescent properties of multilayer (nc-Si–SiO_x–SiO_y)_n nanostructures with porous barrier layers. Applied Nanoscience. 2020; 10(12): 4695-4701. doi: 10.1007/s13204-020-01404-z

8.

8.         Michailovska, KV, Indutnyi, IZ, Shepeliavyi, PE, et al. Formation of silicon nanocomposites by annealing of (SiO_x/Sm)_n multilayers: luminescence, Raman and FTIR studies. Applied Nanoscience. 2023; 13(11): 7187-7194. doi: 10.1007/s13204-023-02887-2

9.

9.         Sarikov A. Thermodynamic theory of phase separation in nonstoichiometric Si oxide films induced by high-temperature anneals. Nanomanufacturing. 2023; 3(3): 293–314. doi: 10.3390/nanomanufacturing3030019

10.

10.      Nayfeh MH. Fundamentals and Applications of Nano Silicon in Plasmonics and Fullerines: Current and Future Trends. Elsevier Publishing, Cambridge, MA; 2018.

11.

11.      Khriachtchev L. Silicon Nanophotonics: Basic Principles, Present Status, and Perspectives. Pan Stanford Publishing; 2016.

12.

12.      Yuan Z, Anopchenko A, Pavesi L. Innovative quantum effects in silicon for photovoltaic applications. In: Pizzini S (editor). Advanced Silicon Materials for Photovoltaic Applications. John Wiley & Sons; 2012. pp. 355–391. doi: 10.1002/9781118312193.ch10

13.

13.      Sopinskyy M, Khomchenko V. Electroluminescence in SiO_x films and SiO_x film-based systems. Curr Opin Solid State Mater Sci. 2003; 7(2): 97–109. doi: 10.1016/S1359-0286(03)00048-2

14.

14.      Bratus’ OL, Evtukh AA, Ievtukh A, et al. Nanocomposite SiO₂(Si) films as a medium for non-volatile memory. Journal of Non-Crystalline Solids. 2008; 354(35-39): 4278-4281. doi: 10.1016/j.jnoncrysol.2008.06.037

15.

15.      Shieh JM, Lai YF, Ni WX, et al. Enhanced photoresponse of a metal-oxide semiconductor photodetector with silicon nanocrystals embedded in the oxide layer. Applied Physics Letters. 2007; 90(5). doi: 10.1063/1.2450653

16.

16.      Evtukh AA, Litovchenko VG, Semenenko MO. Electrical and emission properties of nanocomposite SiO_x(Si) and SiO₂(Si) films. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena. 2006; 24(2): 945-949. doi: 10.1116/1.2183787

17.

17.      Yao J, Sun Z, Zhong L, et al. Resistive switches and memories from silicon oxide. Nano Letters. 2010; 10(10): 4105-4110. doi: 10.1021/nl102255r

18.

18.       Mehonic A, Shluger AL, Gao D, et al. Silicon oxide (SiO_x): A promising material for resistance switching? Advanced Materials. 2018; 30(43). doi: 10.1002/adma.201801187

19.

19.      Chen W, Fang R, Balaban MB, et al. A CMOS-compatible electronic synapse device based on Cu/SiO₂/W programmable metallization cells. Nanotechnology. 2016; 27(25): 255202. doi: 10.1088/0957-4484/27/25/255202

20.

20.      Ugwumadu C, Subedi KN, Thapa R, et al. Structure, vibrations and electronic transport in silicon suboxides: Application to physical unclonable functions. Journal of Non-Crystalline Solids: X. 2023; 18: 100179. doi: 10.1016/j.nocx.2023.100179

21.

21.      Lisovskyy IP, Indutnyy IZ, Gnennyy BN, et al. Structural-phase transformations in SiO_x films in the course of vacuum heat treatment. Semiconductors. 2003; 37(1): 97–102. doi: org/10.1134/1.1538546

22.

22.      Zacharias M, Heitmann J, Scholz R, et al. Size-controlled highly luminescent silicon nanocrystals: A SiO/ SiO₂ superlattice approach. Applied Physics Letters. 2002; 80(4): 661-663. doi: 10.1063/1.1433906

23.

23.      Szekeres A, Nikolova T, Paneva A, et al. Silicon clusters in silicon monoxide films. Journal of Optoelectronics and Advanced Materials. 2005; 7(3): 1383–1387.

24.

24.      Garrido Fernandez B, Lopez M, Garcıa C, et al. Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO₂. Journal of Applied Physics. 2002; 91(2): 798-807. doi: 10.1063/1.1423768

25.

25.      Sopinskii NV, Khomchenko VS, Litvin OS, et al. Properties of low-refractive-index films obtained by the close-spaced vapor transport technique under the sublimation of graphite in a quasi-closed volume. Technical Physics. 2011; 56(11): 1665-1669. doi: 10.1134/s1063784211110259

26.

26.      Nakamura M, Mochizuki Y, Usami K, et al. Infrared absorption spectra and compositions of evaporated silicon oxides (SiO_x). Sol St Commun. 1984; 50(12): 1079–1081. doi: 10.1016/0038-1098(84)90292-8

27.

27.      Raciti R, Bahariqushchi R, Summonte C, et al. Optical bandgap of semiconductor nanostructures: Methods for experimental data analysis. Journal of Applied Physics. 2017; 121(23). doi: 10.1063/1.4986436

28.

28.      Cody GD. Urbach edge of crystalline and amorphous silicon: a personal review. J. Non-Cryst. Solids. 1992; 141: 3–15. doi: 10.1016/S0022-3093(05)80513-7

29.

29.      O’Leary SK, Johnson SR, Lim PK. The relationship between the distribution of electronic states and the optical absorption spectrum of an amorphous semiconductor: An empirical analysis. Journal of Applied Physics. 1997; 82(7): 3334-3340. doi: 10.1063/1.365643

30.

30.      Saito K, Ikushima AJ. Absorption edge in silica glass. Physical Review B. 2000; 62(13): 8584-8587. doi: 10.1103/physrevb.62.8584

31.

31.      Tauc J, Grigorovici R, Vancu A. Optical properties and electronic structure of amorphous germanium. Phys. Status Solidi B. 1966; 15(2): 627–637. doi: 10.1002/pssb.19660150224

32.

32.      Freeman EC, William P. Optical constants of rf sputtered hydrogenated amorphous Si. Physical Review B. 1979; 20(2): 716-728. doi: 10.1103/physrevb.20.716

33.

33.      Persans PD, Ruppert AF, Chan SS, et al. Relationship between bond angle disorder and the optical edge of a-Ge:H. Solid State Commun. 1984; 51(4): 203–207. doi: 10.1016/0038-1098(84)90996-7

34.

34.      Cody GD, Tiedje T, Abeles B, et al. Disorder and the optical-absorption edge of hydrogenated amorphous silicon. Physical Review Letters. 1981; 47(20): 1480-1483. doi: 10.1103/physrevlett.47.1480

35.

35.      Grein CH, John S. Temperature dependence of the Urbach optical absorption edge: A theory of multiple phonon absorption and emission sidebands. Physical Review B. 1989; 39(2): 1140-1151. doi: 10.1103/physrevb.39.1140

36.

36.      Bondi RJ, Lee S, Hwang GS. First-principles study of the mechanical and optical properties of amorphous hydrogenated silicon and silicon-rich silicon oxide. Physical Review B. 2010; 81(19). doi: 10.1103/physrevb.81.195207

37.

37.      Bratus’ VY, Yukhimchuk VA, Berezhinsky LI, et al. Structural transformations and silicon nanocrystallite formation in SiO_x films. Semiconductors. 2001; 35(7): 821–826. doi: 10.1134/1.1385719

38.

38.      Nikolenko AS, Sopinskyy MV, Strelchuk VV, et al. Raman study of Si nanoparticles formation in the annealed SiO_x and SiO_x:Er,F films on sapphire substrate. J Optoelectron Adv Mater. 2012; 14(1–2): 120–124.

39.

39.      Sarikov A. Crystallization behaviour of amorphous Si nanoinclusions embedded in silicon oxide matrix. Phys. Status Solidi A. 2019; 217(4): 1900513. doi: org/10.1002/pssa.201900513

40.

40.      Lisovskyy IP, Voitovich MV, Sarikov AV, et al. Transformation of the structure of silicon oxide during the formation of Si nanoinclusions under thermal annealings. Ukr J Phys. 2009; 54(4): 383–390.

41.

41.      Lee BG, Hiller D, Luo JW, et al. Strained interface defects in silicon nanocrystals. Advanced Functional Materials. 2012; 22(15): 3223-3232. doi: 10.1002/adfm.201200572

42.

42.      Ballester M, Márquez AP, García-Vázquez C, et al. Energy-band-structure calculation by below-band-gap spectrophotometry in thin layers of non-crystalline semiconductors: A case study of unhydrogenated a-Si. Journal of Non-Crystalline Solids. 2022; 594: 121803. doi: 10.1016/j.jnoncrysol.2022.121803

43.

43.      Askari S, Svrcek V, Maguire P, et al. The interplay of quantum confinement and hydrogenation in amorphous silicon quantum dots. Advanced Materials. 2015; 27(48): 8011-8016. doi: 10.1002/adma.201503013

44.

44.      Collins RW, Koh J, Ferlauto AS, et al. Real time analysis of amorphous and microcrystalline silicon film growth by multichannel ellipsometry. Thin Solid Films. 2000; 364(1–2): 129–137. doi: 10.1016/S0040-6090(99)00925-6

45.

45.      Abdulraheem Y, Gordon I, Bearda T, et al. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD. AIP Advances. 2014; 4(5): 057122. doi:10.1063/1.4879807

46.

46.      Nikitin T, Velagapudi R, Sainio J, et al. Optical and structural properties of SiO_x films grown by molecular beam deposition: Effect of the Si concentration and annealing temperature. Journal of Applied Physics. 2012; 112(9). doi: 10.1063/1.4764893