Stretchable, Transparent Zinc Oxide Thin Film Transistors

Abstract

Stretchable and transparent thin film transistors (TFTs) with intrisically brittle oxide semiconductors are built using a wavy structural configuration that can provide high flexibility and stretchability. After device fabrication procedures including high temperature annealing, the oxide semiconductor‐based TFT arrays can be transferred directly to plastic or rubber substrates, without an additional device process, using transfer printing methods. This procedure can avoid some of the thermal degradation problems associated with plastic or rubber substrates by separating them from the annealing procedure needed to improve the device performance. These design and fabrication methods offer the possibility of developing a new format of stretchable electronics.

Metal oxide semiconductor thin-film transistors for flexible electronics

“…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. 78,132,147,205 An alternative to polymers is constituted by metal foils, such as Al foils, 156 and stainless steel substrates.…”

“…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. 78,132,147,205 An alternative to polymers is constituted by metal foils, such as Al foils, 156 and stainless steel substrates. 148 The main benefit of metal foils is the high T m (above 1000 C in the case of stainless steel).…”

“…Finally, mechanically active multilayer substrates using a highly cross-linked hydrogel swelling layer and a stiff PI have been shown. Typical adhesion or buffer layers are made of silicon nitride (SiN x ), 92,106,113,114,140,[143][144][145][146]150,151,173,182,183 silicon oxide (SiO x ), 78,82,135,148,154,157,168,170,181,205 and photoresist sandwiched between SiN x and SiO x . 158 Organic materials, 78,82,136,148,154,157,168,170,181,205 in particular, SU8, 153 or PVP is especially well-suited as smoothing layers.…”

“…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.…”

“…Remarkably, in 2007 Ju et al showed the first flexible and solution-processed metal oxide semiconductor TFTs based on ZnO and In 2 O 3 NWs. 76 From 2008, tremendous advances were made in the field of flexible devices, from IGZO TFTs on cellulose fiber-based paper, 77 stretchable and transparent ZnO TFTs, 78 complementary inverters based on n-type IGZO and ptype SnO TFTs with and on paper, 79 ultraflexible and transparent IGZO TFTs, 80 three-dimensionally (3D) conformable IGZO TFTs and circuits, 81 water soluble IGZO TFTs, 82 to mechanically active biomimetic IGZO TFTs. 23 Nowadays, the state-of-the-art flexible IGZO TFTs yield excellent electrical performance with carrier mobility values up to 84 cm 2 V À1 s…”