Influence of dielectric overlayers on self-heating of a microdisk laser

We studied experimentally and numerically self-heating of a microdisk laser developed in the AlGaInAs material system and covered with dielectric layers. By experiments, we found that planarization of the microlaser with SU-8 photoresist significantly (almost, 2-fold) decreases the microlaser thermal resistance. Calculations demonstrate that a downward heat flux through the substrate to the heat sink is a dominant way of heat dissipation, and upward convection is much less relevant. Also, the calculations showed that covering microlaser with a TiO2 layer barely affects microdisk temperature but decreases heat localization in the structure.

Effect of Iron Content on Corrosion Properties of Pure Titanium as Grain Refiner

Microstructures and corrosion properties of pure titanium were characterized when iron was used as a grain refiner. The added Fe element acted as a strong grain refiner for pure titanium by forming β Ti phase at grain boundaries, and 0.15 wt% Fe was revealed to be a sufficient amount to make the grain size of pure titanium below 20 μm, which was the requirement for the desired titanium cathode. However, corrosion resistance was decreased with the Fe amount added. From the open circuit potential (OCP) results, it was obvious that the TiO2 stability against the reducing acid environment was deteriorated with the Fe amount, which seemed to be the main reason for the decreased corrosion resistance. Electrochemical impedance spectroscopy (EIS) results showed that both the decrease in the compact oxide film’s resistance (Rb) and the appearance of the outer porous film occurred as a result of the dissolution of the TiO2 layer, whose phenomena became more apparent as more Fe was added.

Preparation of Dye-Sensitized Solar Cell (DSSC) Using TiO2 and Mahkota Dewa Fruit (Phaleria Macrocarpa (Scheff) Boerl.) Extract

A dye sensitized solar cell (DSSC) is a low-cost solar cell with attractive features. DSCC contains of photoelectrode, dye, electrolyte, and counter electrode with photoelectrochemical system. The aim of this research is to determine the percent efficiency produced by DSSC from the Mahkota Dewa extract. This was carried out in various stages, namely sample preparation and extraction, DSSC assembly, TiO2 characterization using Scanning Electron Microscopy (SEM), and testing its current and voltage. The results showed that the maximum wavelength of the Mahkota Dewa extract dye test using a UV-Vis spectrophotometer was 554 nm with an absorbance of 0.163, which was believed to be the wavelength of flavonoid and anthocyanin compounds. Based on the characterization results, surface morphology was spherical and agglomerated. However, after being soaked in the dye, the surface morphology of the TiO2 layer did not appear spherical on the surface that was expected to have been covered by the dye. The measurement using sunlight sources showed that the maximum current and voltage of DSSC with a concentration of 30% w/v was 21.8x10-4A and 58.86 V with an efficiency of 22.43x10-3 %. In addition, there was a 0.482% decrease in DSSC efficiency based on the storage time which lasted for a period of 6 days.