Cet ouvrage fait partie de la bibliothèque YouScribe
Obtenez un accès à la bibliothèque pour le lire en ligne
En savoir plus

Application of p electron theory to predict new materials for rewritable optical recording [Elektronische Ressource] / vorgelegt von Daniel Muturi Wamwangi

195 pages
Application of p electron theory to predict newmaterials for rewritable optical recordingVon der Fakultat fur Mathematik, Informatik und˜ ˜Naturwissenschaften der Rheinisch-Westfalischen Technischen˜Hochschule Aachen zur Erlangung des akademischen Grades einesDoktors der Naturwissenschaften genehmigte DissertationVorgelegt vonDaniel Muturi WamwangiM.Sc.aus Nairobi, KeniaBerichter: Universitatsprofessor Dr. Matthias Wuttig˜Universita˜tsprofessor Dr. Jean GeurtsTag der mundlichen Prufung: 28. Mai 2004˜ ˜Diese Dissertation ist auf den Internetseiten derHochschulbibliothek online verfugbar˜Gedruckt mit Unterstut˜ zung des Deutschen Akademischen Austauschdientes2ContentsList of Tables VList of Figures VI1 Introduction 22 Technological aspects of phase change recording 42.1 Main issues in optical data storage . . . . . . . . . . . . . . . . . . . . . . 42.1.1 Review of the current trends in optical data storage . . . . . . . . . 82.1.2 Material design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.1.3 Statement of the problem and objectives of this work. . . . . . . . . 152.1.4 Summary and Layout of Thesis . . . . . . . . . . . . . . . . . . . . 153 Theoretical background 173.1 Thermal Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.1.1 Evaporation of alloys . . . . . . . . . . . . . . . . . . . . . . . . . . 223.2 Scattering of X-rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.2.
Voir plus Voir moins

Application of p electron theory to predict new
materials for rewritable optical recording
Von der Fakultat fur Mathematik, Informatik und˜ ˜
Naturwissenschaften der Rheinisch-Westfalischen Technischen˜
Hochschule Aachen zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften genehmigte Dissertation
Vorgelegt von
Daniel Muturi Wamwangi
M.Sc.
aus Nairobi, Kenia
Berichter: Universitatsprofessor Dr. Matthias Wuttig˜
Universita˜tsprofessor Dr. Jean Geurts
Tag der mundlichen Prufung: 28. Mai 2004˜ ˜
Diese Dissertation ist auf den Internetseiten der
Hochschulbibliothek online verfugbar˜Gedruckt mit Unterstut˜ zung des Deutschen Akademischen Austauschdientes
2Contents
List of Tables V
List of Figures VI
1 Introduction 2
2 Technological aspects of phase change recording 4
2.1 Main issues in optical data storage . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 Review of the current trends in optical data storage . . . . . . . . . 8
2.1.2 Material design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.3 Statement of the problem and objectives of this work. . . . . . . . . 15
2.1.4 Summary and Layout of Thesis . . . . . . . . . . . . . . . . . . . . 15
3 Theoretical background 17
3.1 Thermal Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.1 Evaporation of alloys . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2 Scattering of X-rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.1 X-ray difiraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.2 Bragg equation and reciprocal lattice . . . . . . . . . . . . . . . . . 28
3.2.3 X-ray re ectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.3 Kinetics of crystallization. . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.3.1 Nucleation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3.2 Crystal growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3.3 Johnson-Mehl-Avrami (JMA model) . . . . . . . . . . . . . . . . . 40
3.4 Lattice energy formalisms to predict crystal structure . . . . . . . . . . . . 42
3.4.1 Structural relaxations and DFT calculations . . . . . . . . . . . . . 42
3.5 Peierls efiect to explain solid structure . . . . . . . . . . . . . . . . . . . . 44
IContents
3.6 Mechanical stress induced in thin fllms . . . . . . . . . . . . . . . . . . . . 46
4 Experimental Methods 49
4.1 Thermal Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.1.1 Knudsen efiusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.2 Composition determination . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.3 Secondary Neutral Mass Spectrometry . . . . . . . . . . . . . . . . . . . . 52
4.3.1 Preparation of reference standards for quantiflcation. . . . . . . . . 56
4.4 Four- point probe method . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.4.1 Activation energy for crystallization . . . . . . . . . . . . . . . . . . 58
4.5 The Philips X’pert MRD system. . . . . . . . . . . . . . . . . . . . . . . . 59
4.5.1 X-ray re ectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.5.2 X-ray difiraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.6 Optical spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.6.1 Interband transitions . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.6.2 Spectroscopic ellipsometry . . . . . . . . . . . . . . . . . . . . . . . 71
4.7 Static tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.8 Atomic Force Microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.9 Mechanical stress by wafer curvature method . . . . . . . . . . . . . . . . . 76
5 Results and discussion 77
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.2 Generalization of concept to AuInTe , AuSnTe and AuSbTe . . . . . . . 782 2 2
5.2.1 AuInTe composition by SNMS . . . . . . . . . . . . . . . . . . . . 792
5.2.2 Electrical characterization of AuInTe . . . . . . . . . . . . . . . . . 792
5.2.3 Stress induced upon crystallization of AuInTe . . . . . . . . . . . . 812
5.2.4 Structure of AuInTe . . . . . . . . . . . . . . . . . . . . . . . . . . 822
5.2.5 Structural relaxation of AuInTe . . . . . . . . . . . . . . . . . . . 852
5.2.6 Density change upon crystallization . . . . . . . . . . . . . . . . . . 87
5.2.7 Crystallization of AuInTe . . . . . . . . . . . . . . . . . . . . . . . 912
5.2.8 Optical characterization of AuInTe . . . . . . . . . . . . . . . . . . 912
5.2.9 Characterization of AuSnTe alloy. . . . . . . . . . . . . . . . . . . 922
5.2.10 Composition of AuSnTe by SNMS . . . . . . . . . . . . . . . . . . 942
5.2.11 Electrical characterization of AuSnTe . . . . . . . . . . . . . . . . 942
5.2.12 Structure of AuSnTe . . . . . . . . . . . . . . . . . . . . . . . . . . 962
5.2.13 Theoretical determination of the structure of AuSnTe . . . . . . . 992
IIContents
5.2.14 Temperature dependence of density for AuSnTe . . . . . . . . . . . 1002
5.2.15 Crystallization and recrystallization of AuSnTe . . . . . . . . . . . 1012
5.2.16 Optical characterisation of AuSnTe . . . . . . . . . . . . . . . . . . 1042
5.2.17 Characterisation of AuSbTe alloy for phase change applications . . 1042
5.2.18 Stoichiometry of AuSbTe by SNMS . . . . . . . . . . . . . . . . . 1062
5.2.19 Electrical characterization of AuSbTe . . . . . . . . . . . . . . . . 1062
5.2.20 Stress change upon annealing AuSbTe . . . . . . . . . . . . . . . . 1072
5.2.21 Structure of AuSbTe . . . . . . . . . . . . . . . . . . . . . . . . . . 1082
5.2.22 Conflguration entropy for the simple cubic and rock salt structure . 113
5.2.23 Density and thickness change of AuSbTe . . . . . . . . . . . . . . 1152
5.2.24 Amorphisation of AuSbTe . . . . . . . . . . . . . . . . . . . . . . . 1192
5.2.25 Recrystallization of AuSbTe . . . . . . . . . . . . . . . . . . . . . . 1212
5.2.26 Optical characterization of AuSbTe . . . . . . . . . . . . . . . . . 1292
5.3 AgSnTe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1292
5.3.1 Composition determination of AgSnTe by SNMS . . . . . . . . . . 1302
5.3.2 Electrical characterization of AgSnTe . . . . . . . . . . . . . . . . 1302
5.3.3 Temperature dependent stress determination of AgSnTe . . . . . . 1312
5.3.4 Structure of AgSnTe . . . . . . . . . . . . . . . . . . . . . . . . . . 1322
5.3.5 Density change of AgSnTe . . . . . . . . . . . . . . . . . . . . . . 1342
5.3.6 Amorphisation of AgSnTe . . . . . . . . . . . . . . . . . . . . . . . 1372
5.3.7 Crystallization of AgSnTe . . . . . . . . . . . . . . . . . . . . . . . 1422
5.3.8 Recrystallization of AgSnTe . . . . . . . . . . . . . . . . . . . . . . 1432
5.3.9 Optical characterization of AgSnTe . . . . . . . . . . . . . . . . . . 1442
5.4 Characterization of In SbTe . . . . . . . . . . . . . . . . . . . . . . . . . . 1463 2
5.4.1 Chemical determination of In SbTe by SNMS . . . . . . . . . . . . 1483 2
5.4.2 Electrical properties of In SbTe . . . . . . . . . . . . . . . . . . . . 1503 2
5.4.3 Mechanical stresses upon crystallization of In SbTe . . . . . . . . . 1513 2
5.4.4 Structure of In SbTe . . . . . . . . . . . . . . . . . . . . . . . . . . 1523 2
5.4.5 Density change of In SbTe upon crystallization . . . . . . . . . . . 1553 2
5.4.6 Recrystallization of In SbTe . . . . . . . . . . . . . . . . . . . . . 1563 2
5.4.7 Optical characterization of In SbTe . . . . . . . . . . . . . . . . . 1603 2
5.5 Summary and conflrmation of the p electron concept . . . . . . . . . . . . 162
5.6 Expansion of volume in Chalcogenide alloys . . . . . . . . . . . . . . . . . 164
IIIContents
6 Conclusion 168
6.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
6.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Bibliography 173
Acknowledgement 181
Lebenslauf 183
IVList of Tables
2.1 Application of blue laser technology for storage market . . . . . . . . . . . 10
2.2 History of phase change material research for an optical memory.. . . . . . 14
5.1 The experimental and simulated 2? positions of the Bragg re exes for the
AuInTe alloy. The error in the ¢2? deviations decreases with increasing2
2?, this is attributed to the higher resolution of the difiractometer. . . . . . 84
5.2 The atomic positions of Te, Au and Sb in the AuInTe . The atomic posi-2
tions are obtained from the crystallographic data handbook [1]. . . . . . . 85
5.3 The experimental and theoretical 2? values and their deviations for
AuSnTe alloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 982
5.4 The atomic positions of Te, Au and Sb in the AuSbTe . . . . . . . . . . . 1102
5.5 Summary of T and E values for several alloys. . . . . . . . . . . . . . . . 151c a
5.6 The experimental and simulated 2? positions of the Bragg re exes for the
In SbTe alloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1533 2
5.7 Average number of s and p valence electrons for Ag- and Au-based Te alloys164
6.1 Theaveragenumberofsandpelectronsasaparametertopredictstructure
of suitable phase change alloys . . . . . . . . . . . . . . . . . . . . . . . . . 169
6.2 Summary of T =T values for several alloys. . . . . . . . . . . . . . . . . . 171g m
VList of Figures
2.1 The principle of phase change recording. . . . . . . . . . . . . . . . . . . . 5
2.2 Roadmap for future optical storage technologies. . . . . . . . . . . . . . . . 9
2.3 The potential impact of the 3-D multilayer optical storage. . . . . . . . . . 11
3.1 DepositiononasurfaceelementdA forasourceinclinedat ’ withrespectr
to surface normal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2 Comparison of thickness proflle obtained after evaporation in the dynamic
and static modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3 The re ection of X-rays from two lattice planes of interplanar spacing d. . 26
3.4 The difiraction event by lattice planes of interplanar spacing d . . . . . . . 29
3.5 Schematicdiagramshowingthere ectionofx-raysattheinterfaceofthree
media with refractive indices, n , n and n . . . . . . . . . . . . . . . . . . 311 2 3
3.6 Schematic representation of a XRR spectra for a single thin fllm deposited
on a Si Substrate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.7 XRR spectrum of a two layer stack showing the interference patterns of
each layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.8 The free energy diagram for two phases, fi and fl of the same compound as
a function of the conflgurational coordinates. . . . . . . . . . . . . . . . . . 35
3.9 The free energy of formation of nuclei as a function of lattice size. . . . . . 37
3.10 Schematic representation of the phase transition from a phase 1 to the
phase 2 across an energy barrier U . . . . . . . . . . . . . . . . . . . . . 39g;12
3.11 Schematic representation of the temperature dependence of nucleation and
growth rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.12 The temperature dependence of nucleation and growth rate for a fast nu-
cleation and growth dominated materials.. . . . . . . . . . . . . . . . . . . 41
…3.13 The opening up of a band gap at k = § due to the distortion of atoms2a
in a one dimensional atomic chain. . . . . . . . . . . . . . . . . . . . . . . 45
VIList of Figures
4.1 The photo of the combinatorial material synthesis system. . . . . . . . . . 50
4.2 Thicknessgradientsdeterminedfortheindividualelementsconstitutingthe
AuSbTe alloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
4.3 X-ray difiraction spectrum of a thin evaporated Au fllm on silicon. . . . . . 53
4.4 Schematic representation of SNMS results for an evaporated Au thin fllm
on Silicon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.5 Schematic representation of an RBS spectrum for an evaporated Au thin
fllm on carbon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.6 Schematic representation of an SNMS system consisting of the primary ion
source gun and mass analyzer units. . . . . . . . . . . . . . . . . . . . . . . 56
4.7 Schematic representation of a 4-point probe setup. . . . . . . . . . . . . . . 58
4.8 Picture of the Materials Research Difiractometer system. . . . . . . . . . . 60
4.9 A schematic diagram illustrating the shape of the rocking curves for a
concave, convex and at sample [ 2] . . . . . . . . . . . . . . . . . . . . . . 61
4.10 Schematic illustration of the efiect of using the knife edge to improve the
proflle of the rocking curve. . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.11 XRRspectrumofaGe Sb Te samplemeasuredafterimplementingaknife4 1 5
edge to the sample. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.12 Schematic representation of the focus and detector circle of the x-ray
difiractometer system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.13 SchematicillustrationoftheBraggBrettanogeometryforwhichthedetec-
tor moves twice as fast as the sample to maintain the ? - 2? condition. . . 65
4.14 Schematic representation of the focus and detector circle of the x-ray
difiractometer system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.15 Schematic representation of direct and indirect transitions. . . . . . . . . . 71
4.16 Principle of ellipsometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.17 Schematic diagram of the far fleld setup . . . . . . . . . . . . . . . . . . . 74
4.18 Schematic diagram of the wafer curvature setup . . . . . . . . . . . . . . . 76
5.1 Schematic representation of an SNMS spectrum to determine the chemical
composition of AuInTe thin fllm. . . . . . . . . . . . . . . . . . . . . . . . 792
5.2 Temperature dependent sheet resistance measurement for 100 nmAuInTe2
measured at a heating rate of 5 K/min. . . . . . . . . . . . . . . . . . . . . 80
5.3 Kissinger plot from which the activation energy of the amorphous to crys-
talline transition is determined for 100 nm AuInTe . . . . . . . . . . . . . . 812
5.4 Stress as a function of temperature for 200 nm AuInTe . . . . . . . . . . . 822
VIIList of Figures
5.5 Grazing incidence X-ray difiraction of amorphous and chalcopyrite struc-
ture of AuInTe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832
5.6 Pictorial view of chalcopyrite structure of the AuInTe . . . . . . . . . . . 862
5.7 StructuralrelaxationsoftheAuInTe revealthatthechalcopyritestructure2
is the most stable structure [3]. . . . . . . . . . . . . . . . . . . . . . . . . 87
5.8 X-ray re ection measurements and simulated spectra for 80 nm thin fllm
of AuInTe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 882
5.9 Shift in the total re ection edge for a AuInTe fllm after annealing. . . . . 892
5.10 Density and thickness change as function of temperature for AuInTe alloy. 902
5.11 PTE diagram to depict the crystallization of as deposited AuInTe . . . . . 922
5.12 Optical contrast for AuInTe alloy calculated from the optical constants2
determined from spectroscopic ellipsometry and transmission data . . . . 93
5.13 The composition in atom % determined by SNMS techniques for the
AuSnTe alloy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 942
5.14 Sheet resistance as a function of temperature for an 114 nm AuSnTe mea-2
sured at 5 K/min. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.15 XRD patterns showing (a) the as deposited amorphous phase (b) the NaCl
phase (c)the phase separation into SnTe and AuSnTe (d) the ultimate2
segregation to SnTe and AuTe . . . . . . . . . . . . . . . . . . . . . . . . . 972
5.16 PTE diagram on the amorphisation of the AuTe alloy. . . . . . . . . . . 981:7
5.17 Pictorial view of the monoclinic AuTe unit cell. . . . . . . . . . . . . . . . 992
5.18 Structural relaxations of NaCl and chalcopyrite structure to establish the
most stable structure for the AuSnTe alloy. . . . . . . . . . . . . . . . . . 1002
5.19 The increase of the total re ection edge towards high angles upon annealing. 101
5.20 XRRspectraofAuSnTe fllmfortheasdepositedandforthesamesample2
– –annealed at 115 C and 130 C.. . . . . . . . . . . . . . . . . . . . . . . . . 102
5.21 Normalised density and thickness change as a function of temperature for
the AuSnTe alloy determined by XRR method. . . . . . . . . . . . . . . . 1032
5.22 Power time efiect diagrams for crystallization and recrystallization of the
AuSnTe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042
5.23 The optical contrast of an 80 nm AuSnTe alloy determined at ‚ = 830 nm.1052
5.24 SNMS spectra showing the chemical composition of AuSbTe . . . . . . . . 1062
5.25 Temperature dependent sheet resistance measurements on 100 nm AuSbTe .1072
5.26 Kissinger plot for AuSbTe with an activation energy of 1.61 § 0.10 eV,2
determined from heating rates of 1.0 K/min, 2.0 K/min and 5.0 K/min. . . 108
VIII