tesi R. Miscioscia.pdf - EleA@UniSA

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112 Exceptions in morphology-mobility relationship process are exclusively due to the nature, the thickness and the interface of the gate dielectric. Thus, being the insulator features the controlled variable; we decided to briefly identify samples by means of an acronym which reminds to the particular dielectric involved in the fabrication. In figure 1, we report materials, thicknesses and identifying acronyms of OTFT varieties in order to make more immediate the measurement interpretation. More in detail, three thicknesses of PMMA dielectric have been deposited by spinning to make explicit the dependence of mobility from gate electric field and the relationship between insulator thicknesses and pentacene morphology. Structure / Role Material Thickness Sample id. Substrate Boron-silicate glass 1mm Gate adhesion layer Chromium 10nm Gate electrode Gold 50nm Gate insulator Channel semiconductor PMMA 114nm, 225nm, 420nm table 1: Fabricated samples materials, thicknesses and acronym ids. PMMA114 PMMA225 PMMA420 CF 4-treated PMMA 225nm PMMA/CF 4 PFTEOS:TEOS 270nm PFTEOS:TEOS PFTEOS:TEOS having a 10nmthick PMMA layer Pentacene (C 22H 14) 273nm 65nm (avg. thickness) S/D electrodes Gold 50nm PFTEOS:TEOS/PMM A Gate contacts have been deposited in standard conditions with fixed planetary substrate holder in an evaporation chamber at the base pressure of 2·10 -7 mbar from 99.99% purity metals by means of thermal evaporation. Chromium has been evaporated with 0.1Å/s rate and gold with an average rate of 0.5 Å/s.
Chapter 4 113 Pentacene islands are formed by vacuum evaporation of C22H14 from a Kurt J. Lesker Al2O3 source provided with an additional hot-lip at the base pressure of 1.2·10 -7 mbar with an average rate of 0.6Å/s. The pentacene material employed as evaporation source has been purchased from Sigma Aldrich and processed without any other purification. Gate masks, island masks and S/D contact masks are changed by breaking the vacuum and opening the evaporator chamber. 3.2.1 PMMA gate-insulators processing PMMA is spin-coated from 4% and 8% (in weight) solutions in toluene solvent. Thus, three different thicknesses of polymeric dielectric have been obtained by varying the spin coating recipe and polymer concentration as reported in table 2. Sample id. PMMA thickness PMMA concentration (w/w) speed (rpm) Time (s) Acceleration (rpsqm) Ra (nm) Rq (nm) PMMA115 114nm 4% 3500 40 1500 1.2 1.9 PMMA225 225nm 4% 1500 40 1000 1.3 1.6 PMMA420 420nm 8% 3000 40 1500 1.2 1.4 table 2: PMMA thickness recipe to obtain three different film thicknesses. Soon after deposition, toluene is drift off the film by thermal annealing on an hot-plate at 100°C for 2hr. 3.2.2 PFTEOS:TEOS gate-insulators processing The materials used to prepare hydrophobic dielectric films are here below enumerated: • Aqueous solution (0.24M) of hydrochloric (HCl) acid • Poly-(methylmethacrylate) (PMMA) (Mw = 120,000Da) purchased from Sigma-Aldrich • Tetraethyl Orthosilicate (TEOS), purchased from Sigma-Aldrich Mw = 208.33Da
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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
Page 67 and 68: Chapter 2 61 figure 31: OTFT realiz
Page 69 and 70: Chapter 2 63 materials, the higher
Page 71 and 72: Chapter 2 65 The effect of the barr
Page 73 and 74: Chapter 2 67 figure 36: potential p
Page 75 and 76: Chapter 2 69 From table 2, it is ea
Page 77 and 78: Chapter 2 71 thermal-budget treatme
Page 79 and 80: 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: Chapter 4 111 3.2 General device st
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 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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