Modification of the Crystalline Structure of ZnO Nanoparticles Embedded Within a SiO2 Matrix due to Thermal Stress Effects

Abstract

Self-assembled nanocrystals of ZnO were embedded within a SiO 2 matrix by a sequential deposit using reactive R.F. sputtering. The ZnO nanoparticles (NP's) were obtained by depositing a very thin layer (~20 nm) of Zn on the bottom of the valleys of a first SiO 2 rough surface and then covered by another SiO 2 layer at 500 °C. The stress produced, due to the cooling process, by the SiO 2 matrix on the ZnO NP's generates an unusual crystalline phase of ZnO. The crystal structure was determined by means of X ray diffraction patterns. The ZnO + SiO 2 composite shows a transmittance higher than 80 % for wavelengths > 450 nm. Optical absorption allows to reveal the character and value of the optical band gap. Vibrational modes of the material were determined by Raman spectroscopy.

Effect of annealing temperature on response time of ZnO photoconductor fabricated using thermal evaporation technique

“…The samples annealed at 400 °C and 600 °C possess hexagonal and unknown phase structures of ZnO, whereas the samples annealed at 800 °C possess hexagonal, unknown and cubic phase structures of ZnO. Similar kind of multiphase ZnO was reported by A Garcia-Sotelo et al [47]. XRD patterns are well-matched with JCPDS No: 21-1486 (unknown structure), JCPDS No: 89-0510 (hexagonal structure) and JCPDS No: 77-0191 (cubic structure).…”

“…The unknown phase is also dominated in crystallite structure. Therefore, growth mechanism of unknown phase is unable to explain in detail according to literature [47]. Figure 6 shows three-dimensional AFM images of ZnOD to ZnOD800.…”

“…The unusual phase may be originated due to tensile stress created by the SiO 2 matrix. When the ZnO sample is cooled down to room temperature, SiO 2 coefficient of lower thermal expansion prevents the freestanding crystalline characteristics which are caused by the existence of stress [47].…”

Solution Combustion Synthesis of Pencil-Shaped ZnO Nanostructures and the Analysis of Their Photocatalytic Properties

“…This observation suggest that crystalline lattice is modified along with the morphological variation of the as obtained ZnO samples with the incorporation of defects in the crystals. 32 The synthesis process is repeated with pH 5 condition, the precursor is not undergoing any combustion processes it gives a gel like material.…”

Исследование Пленок Оксида Кремния, Имплантированных Цинком

“…На сегодняшний день ведется исследование мемристоров на основе широкого набора оксидов переходных металлов (TiO 2 , HfO 2 , ZrO 2 и др.) [12][13][14].…”