RESUMO
Graphene-metal contact is crucial to fabricate high-performance graphene photodetectors since the external quantum efficiency (EQE) of the photodetector depends on the contact properties, and the influence of the contact properties is particularly dominant in short channel devices for high-speed applications. Moreover, junction properties between the channel graphene and graphene near the contact are also important to analyze the photoresponse because the built-in electric field in the junction determines the EQE of the photodetector. In this study, we investigated a relation between the photoresponse and the built-in electric field induced from the doping level difference in the junction between the channel graphene and graphene near the contact. The photoresponse could be enhanced with a high junction barrier height that is tuned by the doping level difference. In addition, we observed that the improved electrical characteristics of channel graphene do not guarantee the enhancement of the photoresponse characteristics of graphene photodetectors.
RESUMO
PURPOSE: There are various causes of ureter calculi, and genetic factors are known to play a role. Interleukin-1ß (IL-1ß) and calcium-sensing receptor (CaSR) genes are related to hypercalciuria, and urokinase is related to the formation of calcium oxalate stones. This study investigated polymorphisms in IL-1ß, CaSR, and urokinase in patients with urolithiasis and healthy controls. MATERIALS AND METHODS: Urolithiasis patients treated at Chung-Ang University Hospital were enrolled from January 2007 to December 2008. The control group of volunteers displayed normal urinalysis findings in the health screening, no stones identified by ultrasonography, and no history of urolithiasis. DNA extracted from peripheral blood was analyzed by the polymerase chain reaction. Patients were genetically screened for mutations in IL-1ß (484 urolithiasis patients, 208 controls), CaSR (433 urolithiasis patients, 197 controls), and urokinase (370 urolithiasis patients, 167 controls). Stone metabolic study was done to see the differences between the metabolic factors and to discern normal genes from polymorphic genes. RESULTS: According to the genotype frequency and allele frequency analysis, there were no statistically significant differences between IL-1ß, CaSR, and urokinase genes. Also, the analysis between genotypes and metabolic factors did not show statistically significant differences between the three genes. CONCLUSIONS: In Korean urolithiasis patients, IL-1ß, CaSR, and urokinase gene polymorphisms do not differ from those of healthy individuals. A larger-scale study is needed to confirm the need for other genetic markers of urolithiasis.
