ABSTRACT
Phototransistor using 2D semiconductor as the channel material has shown promising potential for high sensitivity photo detection. The high photoresponsivity is often attributed to the photogating effect, where photo excited holes are trapped at the gate dielectric interface that provides additional gate electric field to enhance channel charge carrier density. Gate dielectric material and its deposition processing conditions can have great effect on the interface states. Here, we use HfO2gate dielectric with proper thermal annealing to demonstrate a high photoresponsivity MoS2phototransistor. When HfO2is annealed in H2atmosphere, the photoresponsivity is enhanced by an order of magnitude as compared with that of a phototransistor using HfO2without annealing or annealed in Ar atmosphere. The enhancement is attributed to the hole trapping states introduced at HfO2interface through H2annealing process, which greatly enhances photogating effect. The phototransistor exhibits a very large photoresponsivity of 1.1 × 107A W-1and photogain of 3.3 × 107under low light illumination intensity. This study provides a processing technique to fabricate highly sensitive phototransistor for low optical power detection.
ABSTRACT
BACKGROUND: Gastric cancer is reported to be one of the leading causes of mortality in Korea. Our aim was to evaluate the clinicopathologic usefulness of cyclin E, p53, E-cadherin and beta-catenin expressions in gastric adenocarcinomas. METHODS: Immunohistochemical staining was performed on the 40 early gastric carcinoma (EGC) cases and 69 advanced gastric carcinoma (AGC) cases to examine the relationship with the clinicopathologic parameters. RESULTS: Cyclin E and p53 expressions were significantly lower in the mucosal or submucosal invasion group compared with those in the muscle invasion and subserosal or serosal invasion groups. Cyclin E expression was significantly higher in the node-positive group compared with that in the node-negative group. The loss of beta-catenin expression was significantly higher in the node-negative group. p53 expression was significantly higher in the intestinal type group than that in the diffuse type group. Loss of E-cadherin expression was significantly higher in the diffuse type group. Cyclin E expression correlates with p53 expression. CONCLUSIONS: The depth of invasion seems to correlate with cyclin E and p53 expressions. Lymph node metastasis may correlate with loss of beta-catenin expression.