Improvements in the bending performance and bias stability of flexible InGaZnO thin film transistors and optimum barrier structures for plastic poly(ethylene naphthalate) substrates

Abstract

Bending characteristics of flexible oxide thin-film transistors could be enhanced by optimizing the barrier layers on the polyethylene naphthalate substrate.

Metal oxide semiconductor thin-film transistors for flexible electronics

“…114,155 Since standard PI exhibits a yellowish to brownish color, other polymeric substrates have been introduced to benefit from their transparency in the visual wavelength range. These materials, which are, in general, also cheaper and more easily available, include PET, 29,69,96,165,171,180,184,188 polyethylene naphthalate (PEN), 38,40,41,134,136,139,149,153,158,163,[166][167][168]173,181,202 polyetheretherketone (PEEK), 203 polycarbonate (PC), 154,157 polypropylene (PP) based synthetic paper, 204 parylene, 80,141 polyethersulfone (PES), 178 water-soluble polyvinyl alcohol (PVA), 82 as well as polydimethylsiloxane (PDMS). 78,132,147,[205][206][207] In particular, PDMS is also stretchable and biocompatible, but at the same time hard to process using standard fabrication techniques.…”

“…RF and RF-magnetron sputtering have been used to deposit IGZO, 23,[80][81][82]96,132,[134][135][136]139,145,147,152,155,156,202,208 IZO, 184 GZO, 188 and ZnO. 59,78,177,178,180 Furthermore, IGZO was also deposited by DC sputtering 133,137,153,160,168 and pulsed DC sputtering.…”

“…40,41,132,136,139,153,[158][159][160]163,[166][167][168][169][170]173,174,202,204 This can either be done using native adhesion forces or utilizing an additional adhesive. Alternatively, a flexible foil can also be mechanically fixed on particularly designed holders using metallic clamps.…”

“…At the same time, a big variety of multi-layer contacts have been developed to combine the advantageous properties of different materials; recent examples are: Ti/ Au, 59,69,81,84,113,140,141,143,146,150,151,[181][182][183] Ni/Au, 79 Mo/ Al, 166,173 Cr/Au, 114 Mo/AlNd, 156 Cr/Au/Cr, 92 Mo/Al/Mo, 153 Ti/Au/Ti, 162 or Ti/IZO. 142 Regarding transparent source/drain contacts, only ITO 29,78,80,106,139,155,158,177,180,188,189,202,204,205 and IZO have been used. 160,171,184 Finally, contacts based on Ti (drain) and graphene (source) in combination with a VTFT structure have been published.…”

“…10 displays the corresponding transfer characteristics showing that although the work function of the various gate metals is different, their influence on the electrical performance of IGZO TFTs is minor. 84 Consequently, a variety of different metals: silver (Ag), 189 Al, 59,132,149,153,174,178,202,204 Au, 38,136,167 Cr, 155 and tantalum nitride (TaN) metal alloys have been used as gate contacts. 154,157,170 Especially for BG TFTs, the adhesion of the gate contact to the flexible substrate appears to be the main concern.…”