Record Mobility in Transparent p-Type Tin Monoxide Films and Devices by Phase Engineering

Abstract

Here, we report the fabrication of nanoscale (15 nm) fully transparent p-type SnO thin film transistors (TFT) at temperatures as low as 180 °C with record device performance. Specifically, by carefully controlling the process conditions, we have developed SnO thin films with a Hall mobility of 18.71 cm(2) V(-1) s(-1) and fabricated TFT devices with a linear field-effect mobility of 6.75 cm(2) V(-1) s(-1) and 5.87 cm(2) V(-1) s(-1) on transparent rigid and translucent flexible substrates, respectively. These values of mobility are the highest reported to date for any p-type oxide processed at this low temperature. We further demonstrate that this high mobility is realized by careful phase engineering. Specifically, we show that phase-pure SnO is not necessarily the highest mobility phase; instead, well-controlled amounts of residual metallic tin are shown to substantially increase the hole mobility. A detailed phase stability map for physical vapor deposition of nanoscale SnO is constructed for the first time for this p-type oxide.

Electroforming-free resistive switching memory effect in transparent p-type tin monoxide

“…It has been reported that Sn interstitials (Sn 2þ i ) and O vacancies (V 2þ 0 ) are the two most common defects present in SnO. 14,15 Hence, we surmise that migration of Sn 2þ i and V 2þ 0 towards the top electrode takes place during the application of negative bias on the top electrode. Furthermore, it is possible that sufficiently large numbers of these positively charged defects are accumulated to the point where a CF that traverses the entire film thickness may be formed at a critical value of negative bias (V SET ).…”

“…Among few p-type oxide materials, tin monoxide (SnO) is attractive owing to its relatively high mobility compared to other p-type oxides, an effect that is due to its hybridized orbitals and increased dispersion at the top of the valence-band. 14,15 There have been no reports on RS behavior in SnO. Therefore, we have investigated the RS effect in SnO and have been able to demonstrate that RS does in fact occur in p-type SnO films.…”

Tin Oxide Based P and N-Type Thin Film Transistors Developed by RF Sputtering

“…Though there are reports of n-channel SnO 2 TFTs, [23][24][25] and pchannel SnO TFTs, [16][17][18][19][20][21][22] there are very few reports of fabrication of both n and p-type TFTs starting from same base material. 22,26,27 An important aspect of tin oxide material is that we can easily achieve ptype (SnO phase) and n-type (SnO 2 phase) conduction in this material.…”

Enhancement of p-type mobility in tin monoxide by native defects

“…On the other hand, V O and Sn i defects, which have a great impact on the hole mobility by modifying the VB, are more likely to appear in Sn-rich environment, thus explaining the increase in hole mobility of SnO grown under such conditions, as observed experimentally. 12,26 A caveat to this is that the presence of defects will also lead to a scattering of the charge carriers such that a high concentration of defects might counteract a high mobility. Therefore, it is important to find a balance between the scattering and the mobility enhancement by electronic modification of the VB edge to obtain an optimal hole mobility.…”