Surface characterization of indium compounds as functional layers for (opto)electronic and sensoric applications [Elektronische Ressource] / von Marcel Himmerlich

Informations

• Publié par: technische_universitat_ilmenau
• Publié le: 01 janvier 2008
• Nombre de lectures: 17
• Langue: English
• Poids de l'ouvrage: 10 Mo

Extrait

Surface characterization of indium compounds
as functional layers for (opto)electronic
and sensoric applications
Dissertation
zur Erlangung des akademischen Grades
doctor rerum naturalium (Dr. rer. nat.)
vorgelegt dem Rat der
Fakult¨at fur¨ Mathematik und Naturwissenschaften
der Technischen Universit¨at Ilmenau
von Dipl.-Ing.
Marcel Himmerlich
aus Waltershausen
Gutachter:
Priv.-Doz. Dr. S. Krischok, Institut fu¨r Physik, Technische Universit¨at Ilmenau
Prof. Dr. O. Ambacher, Fraunhofer-Institut fur¨ Angewandte Festk¨orperphysik, Freiburg
Prof. Dr. T.A. Klar, Institut fur¨ Physik, Technische Universit¨at Ilmenau
Tag der Einreichung: 26.06.2008
Tag der ¨offentlichen Aussprache: 05.11.2008
urn:nbn:de:gbv:ilm1-2008000246Contents
1 Introduction and motivation 1
2 Experimental: setup, methods and physical principles 3
2.1 Thin film growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Reflection high-energy electron diffraction (RHEED) . . . . . . . . . . . . . 5
2.3 Photoelectron spectroscopy (PES) . . . . . . . . . . . . . . . . . . . . . . . 7
2.3.1 Theory of photoelectron emission . . . . . . . . . . . . . . . . . . . . 9
2.3.2 X-ray photoelectron spectroscopy (XPS) . . . . . . . . . . . . . . . . 11
2.3.3 Ultra-violet photoelectron spectroscopy (UPS) . . . . . . . . . . . . 11
2.3.4 Secondary electron emission (SEE) . . . . . . . . . . . . . . . . . . . 12
2.4 Electron energy loss spectroscopy (EELS) . . . . . . . . . . . . . . . . . . . 13
2.5 Excitation sources and electron detection . . . . . . . . . . . . . . . . . . . 14
2.5.1 X-ray source for XPS . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5.2 HIS13 VUV light source for UPS . . . . . . . . . . . . . . . . . . . . 15
2.5.3 EKF 1000 electron source for EELS . . . . . . . . . . . . . . . . . . 16
2.5.4 Hemispherical electron analyzer . . . . . . . . . . . . . . . . . . . . . 17
2.6 Atomic force microscopy (AFM) . . . . . . . . . . . . . . . . . . . . . . . . 18
2.7 Growth and surface analysis system . . . . . . . . . . . . . . . . . . . . . . 21
2.7.1 MBE growth and surface preparation chamber . . . . . . . . . . . . 21
2.7.2 Surface analysis chamber . . . . . . . . . . . . . . . . . . . . . . . . 22
2.7.3 Load lock chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.7.4 Experimental details and specifications of the electron spectroscopy
measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3 Chemical and electronic properties of InN(0001) surfaces 25
3.1 InN - a promising narrow band gap material . . . . . . . . . . . . . . . . . . 25
3.2 Electron accumulation at InN surfaces . . . . . . . . . . . . . . . . . . . . . 26
3.3 Examination of InN surfaces which have been exposed to ambient conditions 27
3.4 Influence of In/N flux ratio on the surface properties of InN grown by PAMBE 29
3.5 Bulk properties of InN(0001) samples grown under optimized conditions . . 37
3.5.1 X-ray diffraction (XRD) . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.5.2 Spectroscopic ellipsometry (SE) . . . . . . . . . . . . . . . . . . . . . 38
3.5.3 High-resolution electron energy loss spectroscopy (HREELS) . . . . 38
3.6 Electronic properties of clean InN(0001) surfaces probed by electron spec-
troscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
ICONTENTS
3.6.1 Occupied and unoccupied electronic states . . . . . . . . . . . . . . . 40
√ √
◦3.6.2 InN(0001)-(2×2) and -( 3× 3)R30 surface states . . . . . . . . . 44
3.6.3 Interaction of InN(0001) with oxygen . . . . . . . . . . . . . . . . . 48
4 Surface properties and ozone interaction of indium oxide films grown by
MOCVD 51
4.1 Indium oxide - an ozone sensitive material at room temperature . . . . . . . 51
4.2 ValencebandstructureandelectronicpropertiesofdifferentIn O polymorphs 532 3
4.3 Non-stoichiometryanddefectstatesinIn O filmsgrownbyMOCVDatlow2 3
temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.4 UV photoreduction and oxidation of LT-InOx sensor surfaces . . . . . . . . 64
5 Surface composition and electronic properties of indium tin oxide and
oxynitride films 73
5.1 Indium tin oxynitride - transparent conductive oxide with improved optical
properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.2 ITO(N) sample preparation and morphology . . . . . . . . . . . . . . . . . 74
5.3 Analysis of the incorporated nitrogen in ITON . . . . . . . . . . . . . . . . 76
5.4 Origin of the thermally induced changes in ITON films . . . . . . . . . . . . 80
5.5 Surface electronic properties of ITON . . . . . . . . . . . . . . . . . . . . . 82
6 Summary and Outlook 87
Bibliography 92
A Abbreviations and Symbols 103
B List of publications 105
IIList of Figures
2.1 Principle setup of the used MBE chamber . . . . . . . . . . . . . . . . . . . 4
2.2 Schematic of the Ewald construction and generation of the RHEED pattern 6
2.3 Surface structure of the uppermost bilayer of wurtzite nitride surfaces with
(0001) orientation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Principle of photoelectron emission . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 Energy dependence of the electron inelastic mean free path for elements . . 10
2.6 Principle components of the monochromated X-ray source . . . . . . . . . . 14
2.7 Functional parts of the HIS13 VUV lamp . . . . . . . . . . . . . . . . . . . 15
2.8 Fal parts of the EKF 1000 electron source . . . . . . . . . . . . . . . 16
2.9 Principle setup of a concentric hemispherical electron analyzer . . . . . . . 17
2.10 Principle of image acquisition in contact mode atomic force microscopy . . 19
2.11 Interatomic force vs. distance curve between tip and sample in atomic force
microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.12 Photographs of the growth and surface analysis system . . . . . . . . . . . . 21
3.1 Contact mode AFM scans and line profiles of an InN surface in the stage of
island coalescence at low thickness . . . . . . . . . . . . . . . . . . . . . . . 28
3.2 Surface band bending and bulk Fermi level of nominally undoped and Mg-
doped InN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.3 Variation of the RHEED patterns of InN films deposited with different In/N
◦flux ratio during PAMBE growth at 440 C . . . . . . . . . . . . . . . . . . 30
3.4 Dependence of the topography of InN films on the In/N flux ratio during
◦PAMBE growth at 440 C measured by non-contact atomic force microscopy 31
3.5 In3d and N1s core level spectra of in-situ prepared InN films . . . . . . . 335/2
3.6 XRD ω-2Θ scans of the InN(0004) reflex comparing InN samples with and
without excess nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.7 Photoemission spectra of the InN valence band and In4d semi-core level
measured using monochromated AlKα radiation . . . . . . . . . . . . . . . 35
3.8 Photoemission spectra of the InN valence band and In4d semi-core level
measured using HeII radiation . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.9 Results of the HREELS measurements on InN(0001) and the corresponding
variation of the carrier plasmon induced energy loss in dependence on the
used primary electron energy . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.10 k-dependence of the detected electron states in PES for different analyzer
acceptance angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
IIILIST OF FIGURES
3.11 Schematic of the different energy regions in a HeI spectrum of InN that
contain information about occupied states below the Fermi level E as wellF
as unoccupied states above the vacuum level E . . . . . . . . . . . . . . 42Vac
3.12 Comparison of the InN density of occupied and unoccupied states between
available DFT calculations and the results of photoemission spectroscopy . 43
3.13 RHEED patterns and geometric atom arrangement of InN(0001) surfaces
√ √
◦with (2×2) and ( 3× 3)R30 reconstruction . . . . . . . . . . . . . . . . 45
√
3.14 Valence band photoemission spectra of InN samples with (2×2) and ( 3×
√
◦3)R30 surface reconstruction as well as indium-rich grown InN . . . . . . 46
3.15 Bulk and surface density of states for InN(0001) with an indium-induced
(2×2) reconstruction and in In-bilayer configuration calculated using DFT . 47
3.16 Changes in the valence band spectra of InN(0001) upon interaction with O 492
4.1 Room temperature ozone detectors based on polycrystalline indium oxide. . 52
4.2 Morphologyofthebcc-In O (001),bcc-In O (111)andrh-In O (0001)sam-2 3 2 3 2 3
ples measured using contact mode atomic force microscopy . . . . . . . . . 54
4.3 In3d and O1s core level spectra of bcc-In O (001), bcc-In O (111) and2 3 2 35/2
rh-In O (0001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552 3
4.4 Valence band photoelectron spectra of bcc-In O (001), bcc-In O (111) and2 3 2 3
rh-In O (0001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562 3
4.5 Model of the band alignment at In O surface depending on different band2 3
gap energies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .