Ferroelectric transistor memory arrays on flexible foils

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.…”

“…A third class of gate dielectrics is ferroelectric materials, in particular, poly(vinylidene fluoridetrifluoroethylene) [P(VDF-TrFE)]. 132,136,149,167 P(VDF-TrFE) can be reversibly polarized and hence used for the fabrication of non-volatile memory TFTs. Interestingly, recently also chicken albumen ferroelectric gate dielectrics have been demonstrated, as shown in Fig.…”

“…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.…”

“…Moreover, also other properties like adhesion or transparency need to be considered. These requirements resulted in the use of different metals: Al, 77,149,152,154,157,165,170,172,179,208 Au, 38,167 Cu, 147 Mo, 41,82,137,138,148,164,168 palladium (Pd), 145 and Ti, 90,93,144,169 whereas Mo and Ti seem to exhibit the lowest specific contact resistance R C . 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, …”

“…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.…”