ОПТИЧЕСКИЕ СВОЙСТВА СИСТЕМЫ ВЕРТИКАЛЬНО УПОРЯДОЧЕННЫХ НАНОВКЛЮЧЕНИЙ КРЕМНИЯ В ОКСИДНОЙ МАТРИЦЕ А.В. Ершов ershov@phys.unn.ruershov@phys.unn.ru 23/3 Gagarin. - презентация

1 ОПТИЧЕСКИЕ СВОЙСТВА СИСТЕМЫ ВЕРТИКАЛЬНО УПОРЯДОЧЕННЫХ НАНОВКЛЮЧЕНИЙ КРЕМНИЯ В ОКСИДНОЙ МАТРИЦЕ А.В. Ершов 23/3 Gagarin Ave., Nizhni Novgorod, RUSSIA

2 Si-NCs-forming by high-temperature annealing of MLS a -Si/SiO 2 Cross-sectional HR TE Microscopy images of Si/SiO 2 MLS after annealing at 1050 С. Si layer thickness (nm): a – 4.2, b – 8.5, с – 20, d – 50 G.F. Grom, et. al. Nature. 407, 358 (2000) D.J. Lockwood, et.al. Phys.Rev.Lett.76, 539(1996)& B.T. Sullivan, et.al. Appl. Phys. Lett. 69, 3149 (1996). Introduction (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) L. Tsybeskov, et.al.,Appl.Phys.Lett.72,4 (1998). M.Zacharias,et.al.,Appl.Phys.Lett.74,2614(1999) 2

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

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

5 Oxide Material k E g (eV) Refractive index Crystallographic Structure SiO 2 Si 3 N 4 Al 2 O 3 TiO 2 HfO 2 ZrO amorphous tetragonal monocline, tetragonal, cubic The frequency dependence of real and imaginary permittivity. Si-Oxide Offsets G.D. Wilk, et. al. J.Appl.Phys.89,5243 (2001)J. Robertson J. Non-Crys. Solids. 303, 94 (2002) On the other hand, the decrease in device dimensions has led to the need for alternative, high dielectric constant ( k ) oxides to replace SiO 2 as the gate dielectric in CMOS devices. Introduction 5

6 Introduction Current investigations of silicon nanocrystals (NCs) are focused on the preparation of assembly of Si quantum dots in SiO 2 host. An original method was established based on the preparation of a -SiO/SiO 2 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- SiO x / high-k -oxide (ZrO 2 or Al 2 O 3 ) multilayered (up to 70 layers) nanoperiodic (period of 5-20 nm) structures (MLSs) prepared by vacuum evaporation are reported. 6

7 ML Structures: a -Si / Al 2 O 3 a -SiO / Al 2 O 3 a -Si / ZrO 2 a -SiO / ZrO 2 a -Si / SiO 2 a -SiO / SiO 2 MLS a- Si( a -SiO x )/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 SiO 2 and sapphire. XRD: period of MLS was measured by PANalitical x'PertPRO X-ray diffractometer HT Annealing: at C (0.5-2 h.) в N 2 -ambindent Ion-doping with doses 9·10 13 – 2·10 17 B + /cm 2 (25 keV) or 9·10 13 – 9·10 16 P + /cm 2 (80 keV) with post-annealing at ºC Hydrogenation: annealing in molecular H 2 (1 atm.) -ambindent up to 600 C (up to 2 h.) Dehydrogenation: annealing in nitrogen ambindent up to 900 C (up to 2 h.) PL spectra of MLS were measured at room temperature by Staford Research Systems SP-150. Emission was excited by N 2 - (337 nm) or Ar- (488 nm) lasers and was detected at nm wavelength band. FTIR transmission spectra were detected by Varian 4100 Excalibur Raman scattering spectra were detected by NTEGRA Spectra System (NT-MDT) excited by 473 nm-solid-state- laser Experimental details 7

8 PERIOD PARAMETERS OF PREPARED MULTILAYERED NANOPERIODIC STRUCTURES a -Si/oxide Sample designation Number of MLS layers Predictable thickness of Si layers of MLS, nm Predictable thickness of oxide layers of MLS, nm XRD period of MLS, nm Total thickness of MLS, nm MLS type Layer thickness, nm a -Si/ZrO 2 3/ a -Si/ZrO 2 4/ a -Si/ZrO 2 8/ a -Si/SiO 2 3/ a -Si/SiO 2 5/ a -Si/SiO 2 5/ a -Si/SiO 2 3/ a -Si/SiO 2 2/52/ Si /Al 2 O 3 3/ ±15 Si /Al 2 O 3 5/ ±15 Si /Al 2 O 3 3/ ±15 Si /Al2O32/ ±15 Si /Al 2 O 3 2/ ±15 XRD data for a- Si/ZrO 2 MLS with 10.1 nm period thickness and 12 period number. Experimental details 8

9 Sample designation Predictable thickness of SiO x layers of MLS, nm Predictable thickness of oxide layers of MLS, nm XRD period of MLS, nm Number of MLS periods Total thickness of MLS, nm MLS type Layer thickness, nm SiO /SiO 2 4/ – SiO /SiO 2 8/ – SiO /SiO 2 2/ – SiO /ZrO 2 4/ SiO /ZrO 2 8/ SiO /ZrO 2 2/ SiO/Al 2 O 3 4/ SiO/Al 2 O 3 8/ SiO/Al 2 O 3 2/ Experimental details PERIOD PARAMETERS OF PREPARED MULTILAYERED NANOPERIODIC STRUCTURES a -SiO x /oxide XRD data for a- SiO x /ZrO 2 MLS with 10.6 nm period thickness and 22 period number. 9

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

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

12 PL spectra of a -SiO x /Al 2 O 3 MLS after annealing at 1100 С exited by N 2 - and Ar – lasers. 1 –4/5 nm; 2 – 7/5 nm; 3 – 11/5 nm PL spectra of a -SiO x /ZrO 2 MLS 4/2 nm (curve 1 ) and 8/2 nm ( 2 ), after annealing at 1000 С. The high-temperature annealing (HTA) at ºC of a - SiO x /ZrO 2 MLS 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. Photoluminescence results 12

13 Comparative PL spectra of a -SiO x /oxide MLS prepared by `optimal` conditions. Photoluminescence results In comparison with PL of NC in MNSs Si/SiO 2 prepared at same conditions, PL intensity was 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. FTIR transmission of ZrO2 film jn silicon substrate annealed at various temperatures. 13

14 Raman scattering spectra of a -Si/ZrO 2 (4/2 nm) and a -SiO x /ZrO 2 (8/2 nm) MLS unannealed ( 1 ) and annealed at 700, 900, 1000 и 1100 С ( 2 – 5, respectively). Sapphire is a substrate! Raman scattering results 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. 14

15 a -SiO x /ZrO 2 Influence of hydrogenation temperature on PL spectra of a -SiO x /ZrO 2 8/2 nm MLS (HTA at 1000 and 1100 ºС). 1 – before hydrogenation, 2 –after hydrogenation, 3 –after hydrogenation (intensity×10) Influence of hydrogenation on PL spectra of a -Si/ZrO 2 4/2 nm MLS (HTA at 1000 and 1100 ºС). 1 – before hydrogenation, and 2 –after hydrogenation a -Si/ZrO С 1100 С PL vs Hydrogenation results 15

16 Influence of hydrogenation and dehydrogenation temperature on PL spectra and intensity ( nm-band) of a -SiO x /Al 2 O 3 11/5 nm MLS (HTA at 1100 ºС) a -SiO x /Al 2 O 3 PL vs Hydrogenation results 16

17 Post-hydrogenation gives rise to enhancement of PL band (~ 500 nm) caused by Si NCs and of nm band associated with (3-5 nm)-NCs of Si, as well Influence of hydrogenation temperature (400 and 500 ºС) on PL spectra of a -SiO x /Al 2 O 3 11/5 nm MLS (HTA at 1100 ºС) PL vs Hydrogenation results 17

18 Typical PL spectra of nc- Si/oxide MLS annealed at 1000 and 1100 С implanted by В + ions with doses, B + /cm 2 : ·10 13, ·10 14, ·10 15, · 10 16, 5 - 2·10 17 and by P + with doses, P + /cm 2 : ( ·10 13, ·10 14, ·10 15, · Photoluminescence by ion-doping results Photoluminescence by ion-doping results 18

19 PL i n tensity vs B + and P + ions dose dependences for nc- Si/SiO 2, nc- Si/ZrO 2, nc- Si/Al 2 O 3 after annealing at 1000, 1100 С. Implantation of boron and phosphorus ions and followed HTA results in quenching of PL. Photoluminescence by ion-doping results Photoluminescence by ion-doping results 19

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 ( °C) annealing (HTA), hydrogenation and thickness values of Si and SiOx layers are given. The PL band at nm from MNSs after the HTA have been determined. In addition, after HTA, the PL band at 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/ZrO 2 system, the NCs radiating at 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 ( °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 ( ) is gratefully acknowledged. 20

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!!! 21