High performance anatase-TiO₂ thin film transistors with a two-step oxidized TiO₂ channel and plasma enhanced atomic layer-deposited ZrO₂ gate dielectric

Abstract

We reported high performance anatase-TiO2 thin film transistors with a two-step oxidized TiO2 channel (O2 annealing and N2O plasma treatment) and O2 plasma enhanced atomic layer-deposited ZrO2 gate dielectric. The transistors using 60 nm TiO2 as the active channel exhibited a steep subthreshold swing of 112 mV dec−1 and a high on/off current ratio of 1.4 × 108. The superior performances, achieved by the two-step oxidizing process and the utilization of ZrO2 as the high-k gate dielectric, show their great potential to be applied in future electronic and optical systems, such as active-matrix displays and ultraviolet sensors.

Large mobility modulation in ultrathin amorphous titanium oxide transistors

“…The μ sat in the device under the discussion was~1.6 × 10 −4 cm 2 V −1 s −1 . While the acquired mobility is lower than the crystalline TiO 2 TFTs reported previously 25,27,29,32 , it is comparable to those reported from the TFTs fabricated using lower crystallinity TiO 2 10,33,37 . We further evaluated the gate dependence of field-effect mobility (μ FE ) using the general expression (Eq.…”

“…TiO 2 as a semiconductor is extensively used in solar cells [17][18][19][20] and photocatalysis [21][22][23][24] , but its application as a TFT channel material has not been much explored. For those reported so far, TiO 2 layers were mostly thicker than~10 nm and crystalline 9,[25][26][27][28][29][30][31][32][33][34] , with only a few reporting the mobility modulation 9,10 . A large extent of mobility modulation, as high as~9 decades, has been recently reported from mixed amorphous-crystalline TiO x TFT 35 , with its origin remaining unexplained nevertheless.…”

Impact of ZrO2 Dielectrics Thickness on Electrical Performance of TiO2 Thin Film Transistors with Sub-2 V Operation

“…Although TiO 2 possesses promising material merits, the reported TiO 2 -based TFTs in literature typically exhibit inferior electrical performance, such as a reduced on/off current ratio ( I on / I off ) and a larger subthreshold swing (SS), compared to that of the InGaZnO counterpart. − This has been true until recently, when we reported TiO 2 TFTs with excellent electrical properties via high temperature O 2 annealing of the TiO 2 channel. We found our TiO 2 TFTs to be comparable to most InGaZnO TFTs, revitalizing the TiO 2 material image for TFT channel usage. , This enhancement is attributed to the passivation effects of the high temperature O 2 annealing on the oxygen vacancy concentration in the TiO 2 , which could have functioned as charge traps in the channel and interface traps at the channel/dielectric interface, leading to the improvement of I on / I off and SS . Most of our attention in our previous work has been focused on the TiO 2 channel and its material properties upon O 2 annealing; the effects of gate dielectrics on the electrical performance of TFTs have not been investigated.…”

“…In this context, economically and ecologically sustainable development necessitates the exploration of alternative Ga and In-free metal oxides . Titanium oxide (TiO 2 ), due to its great chemical and mechanical stability, nontoxicity, low-cost growth method, and earth abundance, could be a potential material solution for cost-effective IoT applications. − …”

“…We found our TiO 2 TFTs to be comparable to most InGaZnO TFTs, revitalizing the TiO 2 material image for TFT channel usage. 30,32 This enhancement is attributed to the passivation effects of the high temperature O 2 annealing on the oxygen vacancy concentration in the TiO 2 , which could have functioned as charge traps in the channel and interface traps at the channel/dielectric interface, leading to the improvement of I on /I off and SS. 33 Most of our attention in our previous work has been focused on the TiO 2 channel and its material properties upon O 2 annealing; the effects of gate dielectrics on the electrical performance of TFTs have not been investigated.…”