Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Discrete charging of traps visualized by scanning gate experiments on a quantum point contact

Abstract: In this paper we apply scanning probe techniques to a QPC patterned with the local anodic oxidation technique on the 2DEG in a GaAs heterostructure. We use the conducting tip of a scanning force microscope as a local gate and measure the conductance of the QPC as a function of tip position. The tip-induced potential locally modifies the microscopic potential landscape close to the constriction. As a consequence, localized charge traps can be discretely charged, leading to a change in the conductance. We find that the QPC is able to detect such charging events related to localized traps placed at distances up to 1 m away from the constriction. The observation of different characteristic functions of the tip-induced potential detected with the QPC, depending on the tip position, confirms that the observed effects are not related to a direct interaction between the scanning tip and the detector, but are mediated by charging at a different location. We also show that there is a direct relation between trap charging and peaked variations in the transmission of the QPC. Our data analysis shows that depending on tip position, the influence of certain charged traps on the conductance can be changed by the presence of the tip, and the modulation of the transmission can be reduced. Transconductance measurements performed at low magnetic field allow us to determine the exact coordinates of trap sites, and to distinguish between charging and discharging of such sites. A similar behavior in space for different sites suggests that electrostatic coupling between sites may be of importance. The determination of the number of traps per area is of importance for transport measurements on semiconductor nanostructures, since charging events may negatively affect the quality of the measured data. We observe a very low density of traps, below 50 per m 2 .

Photon mechanism of image smearing in integrated QWIP-LED pixelless devices

Abstract: An analytical model of an integrated quantum-well infrared photodetector (QWIP) and light-emitting diode (LED) operating as a pixelless image up-converter is developed and used to estimate the device performance. It is shown that the reabsorption of the near-infrared photons trapped in the LED due to total internal reflection and their reemission can significantly influence the quality of the output image.

Electrodeposition and characterization of pH transformed Cu2O thin films for electrochemical sensor

Abstract: Cuprous oxide (Cu2O) thin films have been deposited on stainless steel substrates through potentiostatic electrodeposition technique. The structure and morphology of these films were characterized by X-ray diffraction and Scanning electron microscopy. The change in hkl plane orientation intensity was observed for thin films deposited at different bath pH. The effect of bath temperature on crystallite size were studied. The optical properties of thin films were analyzed by using UV–Visible spectroscopy. The change in band gap with bath pH have been investigated. From Raman spectroscopy only single phase Cu2O peaks have been observed. The current of Cu2O thin films changes with scan rate and concentration of glucose. For 4 mM glucose the maximum current was observed. The results shows that the sensitivity of Cu2O thin films increases with concentration of glucose. Finally, Cu2O thin films shows high glucose sensing at room temperature.