Highly Conductive and Transparent AZO Films Fabricated by PLD as Source/Drain Electrodes for TFTs.

Aluminum-doped ZnO (AZO) has huge prospects in the field of conductive electrodes, due to its low price, high transparency, and pro-environment. However, enhancing the conductivity of AZO and realizing ohmic contact between the semiconductor and AZO source/drain (S/D) electrodes without thermal annealing remains a challenge. Here, an approach called pulsed laser deposition (PLD) is reported to improve the comprehensive quality of AZO films due to the high energy of the laser and non-existence of the ion damage. The 80-nm-thick AZO S/D electrodes show remarkable optical properties (transparency: 90.43%, optical band gap: 3.42 eV), good electrical properties (resistivity: 16 × 10-4 Ω·cm, hall mobility: 3.47 cm²/V·s, carrier concentration: 9.77 × 1020 cm-3), and superior surface roughness (Rq = 1.15 nm with scanning area of 5 × 5 µm²). More significantly, their corresponding thin film transistor (TFT) with low contact resistance (RSD = 0.3 MΩ) exhibits excellent performance with a saturation mobility (µsat) of 8.59 cm²/V·s, an Ion/Ioff ratio of 4.13 × 106, a subthreshold swing (SS) of 0.435 V/decade, as well as good stability under PBS/NBS. Furthermore, the average transparency of the unpatterned multi-films composing this transparent TFT can reach 78.5%. The fabrication of this TFT can be suitably transferred to transparent arrays or flexible substrates, which is in line with the trend of display development.

Effect of Source/Drain Electrodes on the Electrical Properties of Silicon⁻Tin Oxide Thin-Film Transistors.

Ultra-high definition displays have become a trend for the current flat plane displays. In this study, the contact properties of amorphous silicon⁻tin oxide thin-film transistors (a-STO TFTs) employed with source/drain (S/D) electrodes were analyzed. Ohmic contact with a good device performance was achieved when a-STO was matched with indium-tin-oxide (ITO) or Mo electrodes. The acceptor-like densities of trap states (DOS) of a-STO TFTs were further investigated by using low-frequency capacitance⁻voltage (C⁻V) characteristics to understand the impact of the electrode on the device performance. The reason of the distinct electrical performances of the devices with ITO and Mo contacts was attributed to different DOS caused by the generation of local defect states near the electrodes, which distorted the electric field distribution and formed an electrical potential barrier hindering the flow of electrons. It is of significant importance for circuit designers to design reliable integrated circuits with SnO2-based devices applied in flat panel displays.

Comparison of Protein Hydrolysis Catalyzed by Bovine, Porcine, and Human Trypsins.

Based on trypsin specificity (for lysines and arginines), trypsins from different sources are expected to hydrolyze a given protein to the same theoretical maximum degree of hydrolysis (DHmax,theo). This is in contrast with experiments. Using α-lactalbumin and ß-casein, this study aims to reveal if the differences among experimental DHmax (DHmax,exp) by bovine, porcine, and human trypsins are due to their secondary specificity. Peptide analysis showed that ∼78% of all the cleavage sites were efficiently hydrolyzed by porcine trypsin, and ∼47 and ∼53% were efficiently hydrolyzed by bovine and human trypsins, respectively. These differences were explained by the enzyme secondary specificity, that is, their sensitivities to the amino acids around the cleavage sites. The DHmax predictions based on the secondary specificity were 4 times closer to the DHmax,exp than the predictions based on trypsin specificity alone (DHmax,theo). Proposed preliminary relations between binding sites and trypsin secondary specificity allow DHmax,exp estimations of tryptic hydrolysis of other proteins.