ABSTRACT
Extreme gradient boosting (XGBoost) is an artificial intelligence algorithm capable of high accuracy and low inference time. The current study applies this XGBoost to the production of platinum nano-film coating through atomic layer deposition (ALD). In order to generate a database for model development, platinum is coated on α-Al2O3 using a rotary-type ALD equipment. The process is controlled by four parameters: process temperature, stop valve time, precursor pulse time, and reactant pulse time. A total of 625 samples according to different process conditions are obtained. The ALD coating index is used as the Al/Pt component ratio through ICP-AES analysis during postprocessing. The four process parameters serve as the input data and produces the Al/Pt component ratio as the output data. The postprocessed data set is randomly divided into 500 training samples and 125 test samples. XGBoost demonstrates 99.9% accuracy and a coefficient of determination of 0.99. The inference time is lower than that of random forest regression, in addition to a higher prediction safety than that of the light gradient boosting machine.
ABSTRACT
To address the increasing demand for multicolor light-emitting diodes (LEDs), a monolithic multicolor LED with a simple process and high reliability is desirable. In this study, organic-inorganic hybrid LEDs with violet and green wavelengths were fabricated by depositing CsPbBr3 perovskite green quantum dots (QDs) as the light-converting material on InGaN-based violet LEDs. As the injection current was increased, the total electroluminescence (EL) intensities of the hybrid LEDs increased, whereas the light-converted green emission efficiency of the CsPbBr3 QDs decreased. The maximum green-to-violet EL spectral intensity ratio of the hybrid LEDs with CsPbBr3 QDs was achieved with the injection current of <10 mA. Moreover, the EL spectral ratio of the green-to-violet emission decreased at an injection current of 100 mA. The light-conversion intensity of the CsPbBr3 QDs decreased linearly as the junction temperature of the hybrid LEDs was increased with increasing injection current, similar to the temperature-dependent photoluminescence degradation of CsPbBr3 QDs. In addition, the junction temperature of the hybrid LED was minimized by pulse injection to suppress the thermal degradation of QDs and increase the light conversion efficiency to green emission. Therefore, the overall emission spectrum color coordinates of the hybrid LEDs exhibited a red shift from violet to blue in the low-current region and a blue shift toward violet as the green emission of the QDs was decreased above 10 mA.
ABSTRACT
Highly crystallized anatase TiO2 nanoparticles were synthesized at a temperature as low as 120 °C through a glycothermal reaction using amorphous titanium hydrous gel as precursor and 1,4-butanediol and water as solvent. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data support that the glycothermal processing method provides a simple low-temperature route for producing highly crystallized anatase TiO2 nanoparticles without pH adjustment. It is demonstrated that the shape and dispersability of TiO2 nanoparticles can be controlled by the reaction conditions, such as the reaction temperature and variation of the volume ratio of 1,4- butanediol/water (B/W). It was observed that TiO2 samples glycothermally prepared at 220 °C and the B/W ratio of 8/0 showed excellent photocatalytic behavior. The high activity is attributed to the high crystallinity and bipyramidal shape of the particles, which have fewer defects and more active {101} surfaces.
