Jung Joon Pyeon

Fabrication of high-performance p-type thin film transistors using atomic-layer-deposited SnO films

Here, we demonstrate high-performance p-type thin film transistors (TFTs) with a SnO channel layer grown by atomic layer deposition (ALD). The performance of the SnO TFTs relies on hole carriers and defects in SnO and near the back-channel surface of SnO as well as the quality of the gate dielectric/SnO interface. The growth of SnO films at a high temperature of 210 °C effectively suppresses the hole carrier concentration, leading to a high on-current/off-current (Ion/Ioff) ratio. In addition, the SnO films grown at 210 °C achieve high field effect mobility (μFE) compared with the SnO films grown at lower temperatures because of their large grain size and lower impurity contents. However, the SnO films grown at 210 °C still contain defects and hole carriers, especially near the back-channel surface. The post-deposition process – back-channel surface passivation with ALD-grown Al2O3 followed by post-deposition annealing at 250 °C – considerably alleviates the defects and hole carriers, resulting in superior TFT performance (Ion/Ioff: 2 × 106, subthreshold swing: 1.8 V dec−1, μFE: ∼1 cm2 V−1 s−1). We expect that the SnO ALD and subsequent process will provide a new opportunity for producing high-performance p-type oxide TFTs.

Control of the initial growth in atomic layer deposition of Pt films by surface pretreatment

The controllability of the nucleation behavior of Pt in atomic layer deposition (ALD) by surface pretreatments with H2O, H2S, and NH3 was investigated. The H2O pretreatment on SiO2 and TiO2 surfaces had little effect on the nucleation of Pt. The H2S pretreatment on the SiO2 and TiO2 surfaces significantly delayed the nucleation of Pt on them, while the NH3 pretreatment on the TiO2 surface led to fluent nucleation of Pt. In particular, a continuous Pt film was successfully formed even at an ultrathin thickness of approximately 2.2 nm by NH3 pretreatment. This work suggests that the pretreatment with H2S and NH3 is an efficient way to control the nucleation of Pt in ALD without the support of any reactive species, such as plasma or O3. Such a strategy enables the easy control of the size and distribution density of Pt nanoparticles for a wide range of applications.