c-Axis Aligned 3 nm Thick In2O3 Crystal Using New Liquid DBADMIn Precursor for Highly Scaled FET Beyond the Mobility-Stability Trade-off.

Oxide semiconductors (OS) are attractive materials for memory and logic device applications owing to their low off-current, high field effect mobility, and superior large-area uniformity. Recently, successful research has reported the high field-effect mobility (µFE) of crystalline OS channel transistors (above 50 cm2 V-1 s-1). However, the memory and logic device application presents challenges in mobility and stability trade-offs. Here, we propose a method for achieving high-mobility and high-stability by lowering the grain boundary effect. A DBADMIn precursor was synthesized to deposit highly c-axis-aligned C(222) crystalline 3 nm thick In2O3 films. In this study, the 250 °C deposited 3 nm thick In2O3 channel transistor exhibited high µFE of 41.12 cm2 V-1 s-1, Vth of -0.50 V, and SS of 150 mV decade-1 with superior stability of 0.16 V positive shift during PBTS at 100 °C, 3 MV cm-1 stress conditions for 3 h.

Characterization of Inkjet-Printed Digital Microfluidics Devices.

Digital microfluidics (DMF) devices enable precise manipulation of small liquid volumes in point-of-care testing. A printed circuit board (PCB) substrate is commonly utilized to build DMF devices. However, inkjet printing can be used to fabricate DMF circuits, providing a less expensive alternative to PCB-based DMF designs while enabling more rapid design iteration cycles. We demonstrate the cleanroom-free fabrication process of a low-cost inkjet-printed DMF circuit. We compare Kapton and polymethyl methacrylate (PMMA) as dielectric coatings by measuring the minimal droplet actuation voltage for a range of actuation frequencies. A minimum actuation voltage of 5.6 V was required for droplet movement with the PMMA layer thickness of 0.2 µm and a hydrophobic layer of 0.17 µm. Significant issues with PMMA dielectric breakdown were observed at actuation voltages above 10 V. In comparison, devices that utilized Kapton were found to be more robust, even at an actuation voltage up to 100 V.

Highly Dense and Stable p-Type Thin-Film Transistor Based on Atomic Layer Deposition SnO Fabricated by Two-Step Crystallization.

Over the past several decades, tin monoxide (SnO) has been studied extensively as a p-type thin film transistor (TFT). However, its TFT performance is still insufficient for practical use. Many studies suggested that the instability of the valence state of Sn (Sn2+/Sn4+) is a critical reason for the poor performance such as limited mobility and low on/off ratio. For SnO, the Sn 5s-O 2p hybridized state is a key component for obtaining p-type conduction. Thus, a strategy for stabilizing the SnO phase is essential. In this study, we employ a variety of analytical methods such as X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and Hall measurement to identify the main contributors to the physical properties of SnO. It is revealed that precision control of the process temperature is needed to achieve both the crystallinity and thermal stability of SnO. In other words, it would be ideal to obtain high-quality SnO thin films at low temperature. We find that atomic layer deposition (ALD) is a quite advantageous process for obtaining high-quality SnO thin films by the following two-step process: (i) growth of highly c-axis oriented SnO at the initial stage and (ii) further crystallization along the in-plane direction by a postannealing process. Consequently, we obtained a highly dense SnO thin film (film density: 6.4 g/cm3) with a high Hall mobility of ∼5 cm2/(V·s). The fabricated SnO TFTs exhibit a field-effect mobility of ∼6.0 cm2/(V·s), which is a quite high value among the SnO TFTs reported to date, with long-term stability. We believe that this study demonstrates the validity of the ALD process for SnO TFTs.

Significance of Pairing In/Ga Precursor Structures on PEALD InGaOx Thin-Film Transistor.

Atomic layer deposition (ALD) is a promising deposition method to precisely control the thickness and metal composition of oxide semiconductors, making them attractive materials for use in thin-film transistors because of their high mobility and stability. However, multicomponent deposition using ALD is difficult to control without understanding the growth mechanisms of the precursors and reactants. Thus, the adsorption and surface reactivity of various precursors must be investigated. In this study, InGaO (IGO) semiconductors were deposited by plasma-enhanced atomic layer deposition (PEALD) using two sets of In and Ga precursors. The first set of precursors consisted of In(CH3)3[CH3OCH2CH2NHtBu] (TMION) and Ga(CH3)3[CH3OCH2CH2NHtBu]) (TMGON), denoted as TM-IGO; the other set of precursors was (CH3)2In(CH2)3N(CH3)2 (DADI) and (CH3)3Ga (TMGa), denoted as DT-IGO. We varied the number of InO subcycles between 3 and 19 to control the chemical composition of the ALD-processed films. The indium compositions of TM-IGO and DT-IGO thin films increased as the InO subcycles increased. However, the indium/gallium metal ratios of TM-IGO and DT-IGO were quite different, despite having the same InO subcycles. The steric hindrance of the precursors and different densities of the adsorption sites contributed to the different TM-IGO and DT-IGO metal ratios. The electrical properties of the precursors, such as Hall characteristics and device parameters of the thin-film transistors, were also different, even though the same deposition process was used. These differences might have resulted from the growth behavior, anion/cation ratios, and binding states of the IGO thin films.

The absence of the clathrin-dependent endocytosis in rod bipolar cells of the FVB/N mouse retina.

The high rate of exocytosis at the ribbon synapses is balanced by following compensatory endocytosis. Unlike conventional synaptic terminals where clathrin-mediated endocytosis (CME) is a predominant mechanism for membrane retrieval, CME is thought to be only a minor mechanism of endocytosis at the retinal ribbon synapses, but CME is present there and it works. We examined the clathrin expression in the FVB/N rd1 mouse, which is an animal model of retinitis pigmentosa. The broadly distributed pattern of clathrin immunoreactivity in the inner plexiform layer was similar in both the control and FVB/N mouse retinas, but the immunoreactive punta within the rod bipolar axon terminals located in the proximal IPL were decreased in number and reduced in size at postnatal days 14 and they came to disappear at postnatal days 21. This preferential decrease of the clathrin expression at ribbon synapses in the rod bipolar cell axon terminals of the FVB/N mouse retina demonstrates another plastic change after photoreceptor degeneration and this suggests that clathrin may be important for normal synaptic function at the rod bipolar ribbon synapses in the mammalian retina.