Measurements

More documents

Recommendations

Info

6.1 Metastable Effects in µc-Si:H Figure 6.8: ESR signal of highly crystalline porous µc-Si:H after storage in air (upper trace), after annealing at T = 160 ◦ C for one hour (middle trace), and after an additional air-exposure. The vertical dotted lines indicate the g-values of g=2.0043 and g=2.0052 and g=1.998. 6.1.3 Reversible Effects in the Electrical Conductivity The changes in the ESR signal described above suggest that reversible effects might also affect the electrical transport. In particular, the emergence of a strong CE signal after annealing the highly crystalline porous material at elevated temperatures (see Fig. 6.8) suggests considerable shifts of the Fermi level, which might also be visible in the electrical conductivity. Fig. 6.9 shows a temperature cycle taken after the material was stored in air atmosphere for about one week. The samples were measured in a temperature range between T = 100K and 450K (•). The material was than kept in vacuum and annealed for 6 hours at T = 450K. Afterwards the dark conductivity σ D (T) has been measured again (△) in the temperature range between T = 450K and 100K. Reversible effects as a result of air-exposure and annealing cycles, as observed in ESR, can also be seen in σ D . The dark conductivity of IC RS = 0.82 material, shown in Fig. 6.9 (a), shows 73
Chapter 6: Reversible and Irreversible Effects in µc-Si:H Table 6.1: Spin densities of the individual resonances of the IC RS = 0.82 material after air-exposure and followed by annealing for one hour at 160 ◦ C in argon. Resonance N S (storage in air) N S (after annealing) N S (air exposure) g=2.0043 1 × 10 16 cm −3 2 × 10 15 cm −3 1 × 10 16 cm −3 g=2.0052 5 × 10 16 cm −3 1 × 10 16 cm −3 5 × 10 16 cm −3 g=1.998−1.996 − 6 × 10 16 cm −3 − considerably lower values after contact with air, over the entire temperature range investigated. After exposing to air the room temperature conductivity decreases by more than one order of magnitude. The conductivity can be restored to its initial values by annealing the material, just like for the changes observed in ESR. However, there is a distinct difference of the electrical dark conductivity σ D between the porous and compact highly crystalline material upon storage in air and annealing steps. As for the highly crystalline porous sample (IC RS = 0.82) the room temperature dark conductivity decreases after storage in air, one can observe the opposite for the compact material, as shown in Fig. 6.9 (b). For the IC RS = 0.71 material the dark conductivity increases upon contact with air. Material prepared at the transition between microcrystalline and amorphous growth does not show any changes upon contact with air or annealing. Again the air-exposure/annealing cycles can be repeated many times without any sign of fatigue. The observed Figure 6.9: Dependence of the temperature dependent dark conductivity σ D (T) on annealing/air-exposure cycles of (a) highly crystalline porous and (b) highly crystalline but compact material. 74
Page 1 and 2:
Forschungszentrum Jülich in der He
Page 4 and 5:
Forschungszentrum Jülich GmbH Inst
Page 6 and 7:
Kurzfassung In der vorliegenden Arb
Page 8 and 9:
Abstract The electronic properties
Page 10 and 11:
Contents 1 Introduction 1 2 Fundame
Page 12 and 13:
CONTENTS C Abbreviations, Physical
Page 14 and 15:
Chapter 1 Introduction Solar cells
Page 16 and 17:
defect states provided that they ar
Page 18 and 19:
Chapter 8: In this chapter, the inf
Page 20 and 21:
Chapter 2 Fundamentals In this firs
Page 22 and 23:
2.2 Electronic Density of States St
Page 24 and 25:
2.2 Electronic Density of States ta
Page 26 and 27:
2.2 Electronic Density of States Fi
Page 28 and 29:
2.3 Charge Carrier Transport influe
Page 30 and 31:
2.3 Charge Carrier Transport functi
Page 32 and 33:
Chapter 3 Sample Preparation and Ch
Page 34 and 35:
3.1 Characterization Methods Figure
Page 36 and 37: 3.1 Characterization Methods Homoge
Page 38 and 39: 3.1 Characterization Methods µ Fig
Page 40 and 41: 3.1 Characterization Methods compar
Page 42 and 43: 3.1 Characterization Methods bution
Page 44 and 45: 3.1 Characterization Methods posite
Page 46 and 47: 3.2 Deposition Technique admixture
Page 48 and 49: 3.3 Sample Preparation 3.3.1 Sample
Page 50 and 51: 3.3 Sample Preparation reverse bias
Page 52 and 53: Chapter 4 Intrinsic Microcrystallin
Page 54 and 55: 4.2 Electrical Conductivity Figure
Page 56 and 57: 4.3 ESR Signals and Paramagnetic St
Page 58 and 59: 4.3 ESR Signals and Paramagnetic St
Page 60 and 61: 4.4 Discussion - Relation between E
Page 62 and 63: 4.4 Discussion - Relation between E
Page 64 and 65: Chapter 5 N-Type Doped µc-Si:H In
Page 66 and 67: 5.2 Electrical Conductivity Figure
Page 68 and 69: 5.4 Dangling Bond Density Figure 5.
Page 70 and 71: 5.5 Conduction Band-Tail States Fig
Page 72 and 73: 5.6 Discussion concentration evalua
Page 74 and 75: 5.7 Summary Figure 5.7: Schematic b
Page 76 and 77: Chapter 6 Reversible and Irreversib
Page 78 and 79: 6.1 Metastable Effects in µc-Si:H
Page 88 and 89: 6.2 Irreversible Oxidation Effects
Page 94 and 95: 6.3 On the Origin of Instability Ef
Page 96 and 97: 6.3 On the Origin of Instability Ef
Page 98 and 99: Chapter 7 Transient Photocurrent Me
Page 100 and 101: 7.2 Transient Photocurrent Measurem
Page 106 and 107: 7.3 Temperature Dependent Drift Mob
Page 108 and 109: 7.4 Multiple Trapping in Exponentia
Page 110 and 111: 7.5 Discussion Table 7.2: Multiple
Page 112 and 113: 7.5 Discussion 7.5.3 The Meaning of
Page 114 and 115: Chapter 8 Schematic Density of Stat
Page 116 and 117: silicon as shown in Fig. 8.1 b, whi
Page 118 and 119: Chapter 9 Summary In the present wo
Page 120 and 121: Appendix A Algebraic Description of
Page 122 and 123: Eq. A.7 then becomes L(t) F = sin(
Page 124 and 125: Appendix B List of Samples Table B.
Page 126 and 127: Table B.3: Parameters of n-type µc
Page 128 and 129: Appendix C Abbreviations, Physical
Page 130 and 131: µ d Drift mobility µ d,h Hole dri
Page 132 and 133: Bibliography [1] E. Becquerel. Mém
Page 134 and 135: BIBLIOGRAPHY [21] D. Will, C. Lerne
Page 136 and 137:
BIBLIOGRAPHY [45] H. Overhof and M.
Page 138 and 139:
BIBLIOGRAPHY [66] P.W. Anderson. Ab
Page 140 and 141:
BIBLIOGRAPHY [93] J.W. Orton and M.
Page 142 and 143:
BIBLIOGRAPHY [121] J.R. Haynes and
Page 144 and 145:
BIBLIOGRAPHY [148] W. Luft and Y.S.
Page 146 and 147:
BIBLIOGRAPHY [170] G.N. Advani, R.
Page 148 and 149:
List of Publications 1. T. Dylla, R
Page 150 and 151:
Acknowledgments At this point, I wa
Page 152 and 153:
Schriften des Forschungszentrums J
Page 154 and 155:
Page 156 and 157:
Page 159:
Forschungszentrum Jülich in der He
show all

Measurements

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?