tesi R. Miscioscia.pdf - EleA@UniSA

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126 Exceptions in morphology-mobility relationship Also in this case the enhanced structural order of the first pentacene monolayers in comparison to the plain sample evidences a general increase of the charge transport and mobility and a peak value at VGS=-11V as it has already been shown for CF4 in figure 8 and references [31]. Finally, if we compare mobility results obtained for treated and untreated dielectrics as in figure 12, and extract grain dimensions statistics from channel’s SEM images, a relationship between maximum mobility and channel morphology can be graphically shown taking also into account values extracted in previous works [24][23] in figure 13. μ (cm 2 /Vs) 0.2 0.1 0.0 -21 -14 -7 0 7 V G (V) PMMA 115nm PMMA 225nm PMMA 420nm PMMA 225nm - CF4 PFTEOS:TEOS/PMMA PFTEOS:TEOS figure 12: gate voltage dependent mobility comparison for PMMA, PMMA/CF4, PFTEOS:TEOS and PFTEOS:TEOS/PMMA devices If we observe the figure 13 (black square symbols), it’s possible to notice a generally increasing trend of charge mobility versus pentacene lateral grain dimension. This behavior is common in large grains semiconductors[3] and the limiting factor is not the grain mobility but, according to the back-to-back Schottky schematization of the grain-to-grain interface, the current flowing through a grain boundary at room temperature is limited by thermionic emission. (eq. 4).
Chapter 4 127 eq. 4 Where represents the electron mean velocity, l the grain length and Eb the activation energy. μ (cm 2 V -1 s -1 ) 1,0 0,8 0,6 0,4 0,2 0,0 -0,2 PFTEOS:TEOS PMMA 400nm PMMA 115nm PMMA 225nm AZ5214E Polystyrene 0,2 0,4 0,6 0,8 1,0 1,2 1,4 Lateral grain size (μm) figure 13: pentacene grain dimension-mobility graph for pentacene OTFTs having the same channel thickness (65nm). If we look at red square symbols (tagged as: “PFTEOS:TEOS” and “PFTEOS:TEOS/PMMA” names) in figure 13, it comes out that PFTEOS:TEOS and PFTEOS:TEOS/PMMA samples do not follow the same trend we noticed for polymeric dielectrics. In more detail, the extremely hydrophobic surface of PFTEOS:TEOS film, interestingly, does not result in great grain dimensions (Wg < 0.2µm); as a second consideration we can state that the application of the buffer layer, similarly to OTFTs known from previously published papers [31] should benefit of high mobilities deriving from very large pentacene grains. For the PFTEOS:TEOS/PMMA sample even if we obtained grains of average dimension 1.3 µm (with peak dimensions of 2µm), POLYIMIDE PFTEOS:TEOS/PMMA
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Università degli Studi di Salerno
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Acknowledgments It is a pleasure to
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In loving memory of my uncle, Profe
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Introduction Nowadays, it has becom
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Introduction 3 The drawbacks of org
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Introduction 5 Artificial Skin (OTF
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Introduction 7 structure has been d
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Chapter 1 Working principles An Org
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Chapter 1 11 1.1 A model for DC beh
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Chapter 1 13 hp. 4) Decoupling betw
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Chapter 1 15 figure 2: integration
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Chapter 1 17 eq. 11 − = Then, bei
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Chapter 1 19 The formula in eq. 18
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Chapter 1 21 and behaves as a resis
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Chapter 1 23 eq. 22 I DS = μ C ins
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Chapter 1 25 In eq. 27, kB is the B
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Chapter 1 27 eq. 30 · Thu
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Chapter 2 A survey on the state of
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Chapter 2 31 emphasizing the role p
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Chapter 2 33 Only after those years
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Chapter 2 35 In fact, usually the m
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Chapter 2 37 Examples of top-gate b
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Chapter 2 39 deposition process of
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Chapter 2 41 region is patterned by
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Chapter 2 43 figure 11: Non-Relief-
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Chapter 2 45 factor analysing, in p
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Chapter 2 47 In literature results,
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Chapter 2 49 It is clear that the c
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Chapter 2 51 In figure 17 the impro
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Chapter 2 53 figure 19: OFET trans-
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Chapter 2 55 figure 22: Comparison
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Chapter 2 57 channel and gate in Pe
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Chapter 2 59 figure 28: Pentacene b
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Chapter 2 61 figure 31: OTFT realiz
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Chapter 2 63 materials, the higher
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Chapter 2 65 The effect of the barr
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Chapter 2 67 figure 36: potential p
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Chapter 2 69 From table 2, it is ea
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Chapter 2 71 thermal-budget treatme
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Chapter 2 73 in particular in OLEDs
Page 81 and 82: Chapter 2 75 One interesting charac
Page 83 and 84: Chapter 2 77 figure 48: electrical
Page 85 and 86: Chapter 2 79 The research on the OE
Page 87 and 88: Chapter 2 81 photolysis). In this p
Page 89 and 90: Chapter 2 83 [26] Facchetti, Wasiel
Page 91 and 92: Chapter 3 Gate-leakages in polymeri
Page 93 and 94: Gate-leakages 87 determined by XRD
Page 95 and 96: Gate-leakages 89 The results are:
Page 97 and 98: Gate-leakages 91 It has to be consi
Page 99 and 100: Gate-leakages 93 figure 8: Output c
Page 101 and 102: Gate-leakages 95 figure 12: electri
Page 103 and 104: Gate-leakages 97 3.4 Advanced circu
Page 105 and 106: Gate-leakages 99 figure 16: SEM ima
Page 107 and 108: Gate-leakages 101 modeled with a co
Page 109 and 110: Gate-leakages 103 eq. 11 • Shadow
Page 111 and 112: Gate-leakages 105 References [1] R.
Page 113 and 114: Chapter 4 Morphology-mobility relat
Page 115 and 116: Chapter 4 109 insulators to increas
Page 117 and 118: Chapter 4 111 3.2 General device st
Page 119 and 120: Chapter 4 113 Pentacene islands are
Page 121 and 122: Chapter 4 115 For the preparation o
Page 123 and 124: Chapter 4 117 figure 3: PFTEOS:TEOS
Page 125 and 126: Chapter Chapter 4 4 119 (a): (a):
Page 127 and 128: Chapter 4 121 3.4 Device’s charac
Page 129 and 130: Chapter 4 123 mobility with the dim
Page 131: Chapter 4 125 As it can be observed
Page 135 and 136: Chapter 4 129 3.4.3 Thermal charact
Page 137 and 138: Chapter 4 131 Ea(eV) 0.50 0.45 0.40
Page 139 and 140: Chapter 4 133 I D (A) 100.0n 80.0n
Page 141 and 142: Chapter 4 135 μ (cm 2 V -1 s -1 )
Page 143 and 144: Chapter 4 137 T MN (K) 2400 2200 20
Page 145 and 146: Chapter 4 139 Such results, supply
Page 147 and 148: Chapter 4 141 References [1] O. D.
Page 149 and 150: Chapter 4 143 [26] P. Palestri, D.
Page 151 and 152: Conclusions In this PhD dissertatio
Page 153 and 154: Introduction 147 characterizing mor
Page 155 and 156: Table of acronyms and symbols Symbo
Page 157: Table of acronyms and symbols _____
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