tesi R. Miscioscia.pdf - EleA@UniSA

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136 Exceptions in morphology-mobility relationship but now it appears evident that samples having PFTEOS:TEOS as a dielectric have higher activation energies respect to the polymeric ones. E A (eV) 0.26 0.24 0.22 0.20 0.18 0.16 0.14 0.12 PFTEOS 270nm TMN=547K PFTEOS:TEOS/PMMA 273nm TMN=526K PMMA 115nm TMN= 2264K PMMA 400nm TMN=694K PMMA 225nm TMN=1685K -16 -14 -12 -10 -8 -6 V GS (V) figure 20: after Ich extraction, activation energies of the charge transport in PMMA and PFTEOS:TEOS samples are compared in the same plot. Meyer-Neldel temperature (TMN) analysis is another task that benefits of channel current extraction. As we know, this factor is bound to the variance of the Gaussian DOS at OSC/dielectric interface [32][33] and then to the structural disorder in the microstructure of the conducting media. The benefit of Esseni’s elaboration is clear if we compare the EMN/tins plots for PMMA samples (figure 21) where it appears that for a given dielectric the Meyer-Neldel energy decreases as film becomes thicker. In other words, the MNE seems to be for PMMA an index of the degree of control on charge channel modulation that the gate electrode effectively has.
Chapter 4 137 T MN (K) 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 100 150 200 250 300 350 400 T K (nm) TMN (After Ig extraction) TMN (as-is) figure 21: dependence of TMN and EMN from pentacene grain dimension in PMMA dielectrics From TMN observation we can deduce that there’s a sharp separation from the behavior of PMMA samples, having a linearly increasing trend of mobility with Meyer-Neldel energy (EMN=kB*TMN) and the PFTEOS:TEOS ones which exhibit the opposite trend (figure 22) but also lower energetic disorder and, consequently, higher absolute values of charge mobility (figure 19). In fact, as reported by Ullah, Fishchuk et Al. [32], in the case of disordered organic semiconductors, the charge transport can be described in terms of incoherent charge hopping. This process is thermally activated giving rise to a MNR-like dependence of charge mobility from temperature. In the cited paper, the Density Of States in the HOMO level band is modeled by Gaussian disorder having amplitude σ which, at elevated temperatures can be estimated approximately from eq. 6 once TMN is extracted and known.
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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
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Chapter 2 75 One interesting charac
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Chapter 2 77 figure 48: electrical
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Chapter 2 79 The research on the OE
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Chapter 2 81 photolysis). In this p
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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 and 132: Chapter 4 125 As it can be observed
Page 133 and 134: Chapter 4 127 eq. 4 Where r
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: Chapter 4 135 μ (cm 2 V -1 s -1 )
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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