оптические свойства системы вертикально упорядоченных нановключений кремния в оксидной матрице

1. оптические свойства системы вертикально упорядоченных нановключений кремния в оксидной матрице А.В. Ершов ershov@phys.unn.ru 23/3 Gagarin Ave., Nizhni Novgorod, RUSSIA

2. Introduction Si-NCs-forming by high-temperature annealing of MLS a-Si/SiO2 G.F. Grom, et. al.Nature. 407, 358 (2000) Cross-sectional HR TE Microscopy images ofSi/SiO2MLS after annealing at 1050 С. Si layer thickness (nm): a – 4.2, b – 8.5, с – 20, d – 50 L. Tsybeskov, et.al.,Appl.Phys.Lett.72,4 (1998). D.J. Lockwood, et.al. Phys.Rev.Lett.76, 539(1996)&B.T. Sullivan, et.al.Appl. Phys. Lett. 69, 3149 (1996). M.Zacharias,et.al.,Appl.Phys.Lett.74,2614(1999) (а) (б) Экспериментально полученная зависимость размеров нанокристаллов кремния от толщины исходных слоев в Si МНС (а) и температура кристаллизации МНС в зависимости от толщины исходных ямных слоев (б)

3. Introduction Si-NCs-forming by high-temperature annealing of MLS a-SiOx/SiO2 M. Zacharias, et.al. Appl.Phys.Lett. 80,661 (2002) L.X. Yi, et.al.Appl.Phys.Lett.,. 81,4248(2002). 2SiOxxSiO2 + (2-x)Si Phase transformations intoa-SiOx/SiO2MLS by annealing A.F. Leier, et.al., Semiconductors 33, 380 (1999) Формирование НК включает: 1. Стадию зародышеобразования (нуклеацию) 2. Стадию пост-нуклеации (рост включений) 3. Стадию созревания (коалесценцию) Normalized PL spectra showing a blue shift correlated with the crystal size.

4. Introduction Future actual applications of nc-Si MLS-systems Solar Cells Optical Gain L. Pavesi, Materials Today. 8, 18 (2005) Electronic non-volatile memories Light diodes T. Creazzo, et al. J. Luminescence, 130, 631 (2010) D. Tsoukalas, et al. Mat.Sci.Eng. B 124, 93 (2005) G.Conibeer, Materials Today. 10, 42 (2007), M.A. Green, Spinger (2006)

5. Introduction On the other hand, the decrease in device dimensions has led to the need for alternative, high dielectric constant (k) oxides to replace SiO2 as the gate dielectric in CMOS devices. Si-Oxide Offsets The frequency dependence of real and imaginarypermittivity. G.D.Wilk,et. al.J.Appl.Phys.89,5243 (2001) J.Robertson J. Non-Crys. Solids. 303, 94 (2002)

6. Introduction Current investigations of silicon nanocrystals (NCs) are focused on the preparation of assembly of Si quantum dots in SiO2 host. An original method was established based on the preparation of a-SiO/SiO2 multilayered nanoperiodic structures (MLS or amorphous superlattices) which enables independent control of size, size distribution, position and density of the NCs. In our report the results of investigations of photoluminescence (PL), Raman scattering and FTIR-spectroscopy of a-Si/high-k-oxide and a-SiOx/high-k-oxide (ZrO2 or Al2O3) multilayered (up to 70 layers) nanoperiodic (period of 5-20 nm) structures (MLSs) prepared by vacuum evaporation are reported.

7. Experimental details MLSa-Si(a-SiOx)/oxide were prepared by evaporation and electron beam evaporation. Substrates were Si (p-Si (100) 12 Ohm cm,n-Si (100) 5 Ohm cm), fussed SiO2 andsapphire. XRD:period of MLS was measured by PANalitical x'PertPRO X-ray diffractometer HT Annealing: at 500− 1100 C (0.5-2 h.) в N2-ambindent Ion-doping with doses 9·1013 – 2·1017 B+/cm2 (25 keV) or 9·1013 – 9·1016 P+/cm2 (80 keV) with post-annealing at 1000 -1100ºC Hydrogenation:annealing in molecular H2 (1 atm.) -ambindentup to600C(up to 2 h.) Dehydrogenation:annealing in nitrogen ambindentup to900C(up to 2 h.) PL spectra of MLS were measured at room temperature by Staford Research SystemsSP-150. Emission was excited by N2- (337nm) orAr- (488 nm) lasers and was detected at 400-850 nm wavelength band. FTIR transmission spectra were detected by Varian 4100 Excalibur Raman scattering spectra were detected by NTEGRA Spectra System (NT-MDT)excitedby 473 nm-solid-state- laser ML Structures: a-Si / Al2O3a-SiO / Al2O3 a-Si / ZrO2a-SiO / ZrO2 a-Si / SiO2a-SiO / SiO2

8. Experimental details Period parameters of prepared multilayered nanoperiodic structures a-Si/oxide XRD data for a-Si/ZrO2 MLS with 10.1 nm period thickness and 12 period number.

9. Experimental details Period parameters of prepared multilayered nanoperiodic structures a-SiOx/oxide XRD data for a-SiOx/ZrO2 MLS with 10.6 nm period thickness and 22 period number.

10. Photoluminescence results PL spectra of a-Si/ZrO2MLS annealed at 1000 and 1100 С. Period, nm: 3/2, 4/2, 8/2 – 1, 2, 3curves, respectively PL spectra of a-SiOx/ZrO2MLS annealed at 1000 and 1100 С. Period, nm: 4/2 (1000С ), 4/2 (1100 С), 8/2 (1000С ), 8/2 (1100 С) – 1, 2, 3, 4 curves, respectively The high-temperature annealing (HTA) at 1000-1100 ºC of a-SiOx/ZrO2MLS results in formation in silicon- contained layers of Si NCs with sizes 3-5 nm . It is not in case of a-Si/ZrO2MLS.

11. FTIR & Photoluminescence results Спектры ИК-пропускания отожженных МНС SiOx/ZrO2 с периодами 8/2 (а) и 4/2 (б) нм Спектры ФЛ МНС SiOx/ZrO2 с периодом 8/2 нм после отжига при возбуждении азотным (слева) и аргоновым (справа) лазерами

12. Photoluminescence results PL spectra of a-SiOx/ZrO2MLS 4/2 nm (curve1) and 8/2 nm (2), after annealing at 1000 С. The high-temperature annealing (HTA) at 1000-1100 ºC of a-SiOx/ZrO2MLS results in formation in silicon- contained layers of Si NCs with sizes 3-5 nm . PL spectra showing a blue shift correlated with the crystal size. PL spectra of a-SiOx/Al2O3MLSafter annealing at 1100 С exited by N2- andAr –lasers.1 –4/5 nm; 2 – 7/5nm; 3 –11/5 nm

13. Photoluminescence results • ComparativePL spectra of a-SiOx/oxide MLS prepared by `optimal` conditions. • FTIR transmission of ZrO2 film jn silicon substrate annealed at various temperatures. In comparison with PL of NC in MNSs Si/SiO2 prepared at same conditions, PL intensity was 25-50 times smaller. The influence of kind of oxide layer material on MNS PL intensity and spectrum is discussed from the view point of chemical interactions which lead to the formation of intermediate silicate layers at heteroboundaries of nanostructure.

14. Raman scattering results Raman scattering spectra ofa-Si/ZrO2 (4/2 nm) anda-SiOx/ZrO2 (8/2 nm) MLS unannealed(1) and annealedat 700, 900, 1000 и 1100 С (2 – 5, respectively). Sapphire is a substrate! Raman scattering of annealed MNSs gives evidence that sizes of Si NCs, which are responsible for visible PL band, are dependent on silicon-contained layer thickness.

15. PL vs Hydrogenation results a-SiOx/ZrO2 Influence of hydrogenation temperature on PL spectra of a-SiOx/ZrO28/2nmMLS (HTA at1000 and 1100 ºС). 1– before hydrogenation, 2 –after hydrogenation, 3–after hydrogenation (intensity×10) a-Si/ZrO2 1000 С 1100 С Influence of hydrogenation on PL spectra of a-Si/ZrO24/2nmMLS (HTA at1000 and 1100 ºС). 1– before hydrogenation, and 2 –after hydrogenation

16. PL vs Hydrogenation results a-SiOx/Al2O3 Influence of hydrogenation and dehydrogenation temperature on PL spectra and intensity (700-900 nm-band) of a-SiOx/Al2O311/5nmMLS (HTA at 1100 ºС)

17. PL vs Hydrogenation results Influence of hydrogenation temperature (400 and 500ºС)on PL spectra of a-SiOx/Al2O311/5nmMLS (HTA at 1100 ºС) Post-hydrogenation gives rise to enhancement of PL band (~ 500 nm) caused by Si NCs and of 750-850 nm band associated with (3-5 nm)-NCs of Si, as well

18. Photoluminescence by ion-doping results Typical PL spectra of nc-Si/oxideMLS annealed at 1000 and 1100С implanted by В+ ions with doses, B+/cm2: 1- 9.4·1013, 2 - 9.4·1014, 3 - 9.4·1015, 4 - 9.4·1016, 5 - 2·1017and byP+with doses, P+/cm2: (1 - 9.4·1013, 2 - 9.4·1014, 3 - 9.4·1015, 4 - 8.9·1016 .

19. Photoluminescence by ion-doping results PL intensity vs B+ and P+ ions dose dependences for nc-Si/SiO2 , nc-Si/ZrO2, nc-Si/Al2O3after annealing at 1000, 1100С. Implantation of boron and phosphorus ions and followed HTA results in quenching of PL .

20. conclusion • The results of investigations of photoluminescence (PL) of a-Si/oxide and a-SiOx/oxide multilayer nanoperiodic (5-10 nm) structures (MLSs) in dependence on high-temperature (1000-1100 °C) annealing (HTA), hydrogenation and thickness values of Si and SiOx layers are given. The PL band at 400-550 nm from MNSs after the HTA have been determined. In addition, after HTA, the PL band at 700-800 nm for a-SiOx/oxide system due to silicon nanocrystals has been revealed. Raman scattering of MNSs gives evidence of formation of Si NCs, which are responsible for size-dependent visible PL band. In a-Si/ZrO2 system, the NCs radiating at 700-800 nm were not formed or they are not radiating. • The results of investigations of photoluminescence of MLS a-SiOx/oxide doped by implantation of boron and phosphorus ions in dependence on high-temperature (1000-1100 °C) annealing (HTA) are reported. Implantation of boron and phosphorus ions and HTA leads to quenching of PL of MLSs. • Support through the Federal Targeted Program “Scientific and pedagogical cadres of innovative Russia” and RFBR project (10-02-00995) is gratefully acknowledged.

21. Спасибо за внимание! Отдельное спасибо коллегам за дискуссии и методическую помощь: Д.И. Тетельбауму, А.Н. Михайлову, И.А. Чугрову, А.И. Белову, В.К. Васильеву, Ю.А. Дудину, С.С. Андрееву, Ю.А. Вайнеру, А.В. Нежданову, А.А. Ершову и Б.Н. Звонкову!!!