Photo-Stable Transparent Nonvolatile Memory Thin-Film Transistors Using In–Ga–Zn–O Channel and ZnO Charge-Trap Layers

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.…”

“…184 Finally, ZnO was sandwiched between two layers of Al 2 O 3 to create a charge trapping layer in the gate dielectric, leading to non-volatile memory TFTs. 139 d. Contacts. This class of materials includes metals and other conductors employed to fabricate gate and source/drain electrodes.…”

“…90 Multi-layer metals offer, in general, a compromise between good adhesion and high conductivity, especially in the case of Ti/Au, 23,96,181 Ti/Cu, 135 Cr/Au, 174 or Ti/Au/Ti gate stacks. 162 Besides metals and metal alloys, ITO, 29,69,78,80,135,139,165,177,180,184,188,205 IZO, 77,79,133,160,208 In 2 O 3 , 171 and aluminum zinc oxide (AZO) have been used to fabricate transparent gate contacts. 93,134 Furthermore, duallayers of metal and ITO 40 or IZO have also been employed.…”

“…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.…”

“…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.…”