ОПТИЧЕСКИЕ СВОЙСТВА СИСТЕМЫ ВЕРТИКАЛЬНО УПОРЯДОЧЕННЫХ

НАНОВКЛЮЧЕНИЙ КРЕМНИЯ В ОКСИДНОЙ МАТРИЦЕ

А.В. Ершов

ershov@phys.unn.ru 23/3 Gagarin Ave., Nizhni Novgorod, RUSSIA 23/3 Gagarin Ave., Nizhni Novgorod, RUSSIA

Si-NCs-forming by high-temperature annealing of MLS a-Si/SiO2

Cross-sectional HR TE Microscopy images of Si/SiO2 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 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)

Cd

TTTT acmaccryst exp)(

L. Tsybeskov, et.al.,Appl.Phys.Lett.72,4 (1998).

M.Zacharias,et.al.,Appl.Phys.Lett.74,2614(1999)

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Phase transformations into a-SiOx/SiO2 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)

2SiOx xSiO2 + (2-x)Si

A.F. Leier, et.al., Semiconductors 33, 380 (1999)

Si-NCs-forming by high-temperature annealing of MLS a-SiOx/SiO2 Introduction 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).

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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 Introduction

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Oxide Material

kEg (eV)

Refractiveindex

Crystallographic Structure

SiO2

Si3N4

Al2O3

TiO2

HfO2

ZrO2

3.979

802525

8.95.18.73.55.77.8

1.452.01.62.21.92.1

amorphousamorphousamorphoustetragonal

monocline, tetragonal, cubicmonocline, 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 SiO2 as the gate dielectric in CMOS devices.

Introduction Introduction

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Introduction 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.

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ML Structures: a-Si / Al2O3 a-SiO / Al2O3 a-Si / ZrO2 a-SiO / ZrO2 a-Si / SiO2 a-SiO / SiO2

MLS a-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 and sapphire.

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.) -ambindent up to 600C (up to 2 h.)

Dehydrogenation: annealing in nitrogen ambindent up to 900C (up to 2 h.)

PL spectra of MLS were measured at room temperature by Staford Research Systems SP-150. Emission was excited by N2- (337 nm) or Ar- (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) excited by 473 nm-solid-state- laser

Experimental details Experimental details

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PERIOD PARAMETERS OF

PREPARED MULTILAYERED

NANOPERIODIC

STRUCTURES

a-Si/oxide

Sample designation

Number of MLSlayers

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, nmMLS type

Layer thickness,

nm

a-Si/ZrO23/2 61 3.0 2.1 5.0 160 15

a-Si/ZrO24/2 53 4.0 2.1 6.1 175 15

a-Si/ZrO28/2 37 8.0 2.1 10.1 190 15

a-Si/SiO23/7 26 3 7 — 125 15

a-Si/SiO25/11 20 5 11 — 165 15

a-Si/SiO25/22 20 5 22 — 250 15

a-Si/SiO23/15 20 3 15 — 190 15

a-Si/SiO22/5 22 2 5 — 80 15

Si /Al2O3 3/7 9 3 7—

55±15

Si /Al2O3 5/10 7 5 10—

55±15

Si /Al2O3 3/13 8 3 13—

55±15

Si /Al2O3 2/10 10 2 10—

55±15

Si /Al2O3 2/20 6 2 20—

55±15XRD data for a-Si/ZrO2 MLS with 10.1 nm period thickness and 12 period number.

Experimental details Experimental details

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Sample designationPredictable thickness

of SiOx layers of MLS, nm

Predictable thickness of oxide layers of MLS, nm

XRD period

of MLS, nm

Number of MLSperiods

Total thickness

of MLS, nmMLS type

Layer thickness,

nm

SiO /SiO2 4/3 4.4 2.8 – 31 220 15SiO /SiO2 8/3 8.4 2.8 – 25 275 15SiO /SiO2 2/3 2.2 2.8 – 32 165 15SiO /ZrO2 4/2 4.4 2.1 6.6 26 180 15SiO /ZrO2 8/2 8.4 2.1 10.6 22 235 15SiO /ZrO2 2/2 2.2 2.1 4.3 37 165 15SiO/Al2O3 4/3 4.4 2.6 7.0 28 200 15SiO/Al2O3 8/3 8.4 2.6 10.9 24 265 15SiO/Al2O3 2/3 2.2 2.6 4.8 40 190 15

Experimental details 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.

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Photoluminescence resultsPhotoluminescence results

PL spectra of a-Si/ZrO2 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/ZrO2 MLS annealed at 1000 and 1100 С. Period, nm: 4/2 (1000С ), 4/2 (1100 С), 8/2 (1000С ), 8/2 (1100 С) – 1, 2, 3, 4 curves, respectively

The high-temperature annealing (HTA) at 1000-1100 ºC of a-SiOx/ZrO2 MLS results in formation in silicon- contained layers of Si NCs with sizes 3-5 nm . It is not in case of a-Si/ZrO2 MLS. 10

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

FTIR & Photoluminescence resultsFTIR & Photoluminescence results

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PL spectra of a-SiOx/Al2O3 MLS after annealing at 1100 С exited by N2 - and Ar –lasers.1 –4/5 nm; 2 – 7/5 nm; 3 – 11/5 nm

PL spectra of a-SiOx/ZrO2 MLS 4/2 nm (curve 1) and 8/2 nm (2), after annealing at 1000 С.

The high-temperature annealing (HTA) at 1000-1100 ºC of a-SiOx/ZrO2 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 resultsPhotoluminescence results

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Comparative PL spectra of a-SiOx/oxide MLS prepared by `optimal` conditions.

Photoluminescence resultsPhotoluminescence results

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.

FTIR transmission of ZrO2 film jn silicon substrate annealed at various temperatures.

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Raman scattering spectra of a-Si/ZrO2 (4/2 nm) and a-SiOx/ZrO2 (8/2 nm) MLS

unannealed (1) and annealed at 700, 900, 1000 и 1100 С (2 – 5, respectively).

Sapphire is a substrate!

Raman scattering resultsRaman 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 .

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a-SiOx/ZrO2

Influence of hydrogenation temperature on PL spectra of a-SiOx/ZrO2 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/ZrO2 4/2 nm MLS (HTA at 1000 and 1100 ºС). 1 – before hydrogenation, and 2 –after hydrogenation

a-Si/ZrO2 1000 С 1100 С

PL vs Hydrogenation resultsPL vs Hydrogenation results

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Influence of hydrogenation and dehydrogenation temperature on PL spectra and intensity (700-900 nm-band) of a-SiOx/Al2O3 11/5 nm MLS (HTA at 1100 ºС)

a-SiOx/Al2O3

PL vs Hydrogenation resultsPL vs Hydrogenation results

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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

Influence of hydrogenation temperature (400 and 500 ºС) on PL spectra of a-SiOx/Al2O3 11/5 nm MLS (HTA at 1100 ºС)

PL vs Hydrogenation resultsPL vs Hydrogenation results

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Typical PL spectra of nc-Si/oxide MLS 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 - 2·1017 and by P+ with doses, P+/cm2: (1 - 9.4·1013, 2 - 9.4·1014, 3 - 9.4·1015, 4 - 8.9·1016 .

Photoluminescence by ion-doping resultsPhotoluminescence by ion-doping results

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PL intensity vs B+ and P+ ions dose dependences for nc-Si/SiO2 , nc-Si/ZrO2 , nc-Si/Al2O3 after annealing at 1000, 1100С.

Implantation of boron and phosphorus ions and followed HTA results in quenching of PL .

Photoluminescence by ion-doping resultsPhotoluminescence by ion-doping results

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CONCLUSIONThe 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.

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Спасибо за внимание!

Отдельное спасибо коллегамза 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!!!

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