Liu Kin Men

Synthesis and characterization of ZnO:Ca2+ prepared by simple solution method

This paper reports the synthesis and characterization of calcium doped zinc oxide by simple solution method. ZnO:Ca2+ was prepared from zinc acetate dehydrate and calcium nitrate tetrahydrate with Ca2+ concentration were 1, 3, 5, 7 and 10 at% of Zn. The obtained sample was characterized by x-ray diffraction, scanning electron microscopy, electron dispersive spectroscopy and photoluminescence spectroscopy. The XRD spectra showed that the obtained samples has a hexagonal wurtzite crystal that rate corresponding to JCPDS 36-1451 diffraction data with a slightly distorted ZnO lattice. The PL spectrum of ZnO:Ca2+ showed high intensity of violet to blue emission.This paper reports the synthesis and characterization of calcium doped zinc oxide by simple solution method. ZnO:Ca2+ was prepared from zinc acetate dehydrate and calcium nitrate tetrahydrate with Ca2+ concentration were 1, 3, 5, 7 and 10 at% of Zn. The obtained sample was characterized by x-ray diffraction, scanning electron microscopy, electron dispersive spectroscopy and photoluminescence spectroscopy. The XRD spectra showed that the obtained samples has a hexagonal wurtzite crystal that rate corresponding to JCPDS 36-1451 diffraction data with a slightly distorted ZnO lattice. The PL spectrum of ZnO:Ca2+ showed high intensity of violet to blue emission.

Optical properties of amorphous silicon quantum dots (a-Si QDs) with various dot size using extended Hückel theory

A high quality amorphous silicon (a-Si) nanostructures has grown experimentally to study the origin of light emission and the quantum confinement effect in a-Si. The quantum confinement effect increases the band gap of material as the size of quantum structure decreases, which results in a blue shift in optical luminescence and energy absorption. Here we demonstrate this effect using extended Huckel method to calculate fundamental band gap and optical absorption energy of a-Si samples with various dot sizes. As result, when the dot size was decreased from 2.2 to 1.0 nm, the absorption spectra peak shifted toward higher energy from 2.278 eV to 3.856 eV.

Improvement on droplet production rate of ultrasonic - nebulizer in spray pyrolysis process

Atomization is an important part in Spray Pyrolysis (SP) process which is applied to synthesize submicron or nano sized particles or to deposit thin film. Ultrasonic Nebulizer (UN) is usually use in SP due to its homogeneous droplets production with size between 1-5 μm. The drawback of the UN is low droplets production rate. In this research, we successfully developed a Digital Ultrasonic Nebulizer (DUN) with high droplets production rate using two ultrasonic traducers with applied frequency of 2.4 MHz. The result of DUN atomization was improved 4-6 fold compare to the conventional UN. The DUN also has an additional digital features such as pushbutton, LCD and microcontroller which is allow to set duration and applied voltage.