Effect of substrate-induced strain on the structural, electrical, and optical properties of polycrystalline ZnO thin films

Abstract

The effect of substrate-induced strain in polycrystalline ZnO thin films on different substrate, e.g., GaN epilayer, sapphire (0001), quartz glass, Si(111)∕SiO2, and glass deposited by sol-gel process, has been investigated by x-ray diffraction, scanning electron microscope, electrical resistivity, and photoluminescence measurements. A strong dependence of orientation, crystallite size, and electrical resistivity upon the substrate-induced strain along the c axis has been found. The results of structural and morphological studies indicate that relatively larger tensile strain exists in ZnO deposited on sapphire and glass, while a smaller compressive strain appears in film deposited on GaN and the strain is relaxed in larger crystallite size. The electrical resistivity of the films increases exponentially with increasing strain. The excitonic peak positions are found to shift slightly towards lower energy side with increasing strain. The analysis shows that GaN being a closely lattice-matched substrate produces ZnO films of better crystallinity with a lower resistivity.

Magnetic-control-electric and reversal behavior of ZnO/NiFe/ZnO multilayer films

“…18 Moreover, it can be observed that the (002) diffraction peak shifted from low angle degree (34.04 • ) to high angle degree (34.16 • ) as shown in the XRD patterns, indicating the internal stress state of the multilayer films changed while inserting a NiFe layer into ZnO. According to previous reports, 19,20 the in-plane biaxial stress in ZnO can be obtained from the following equation: where c and c 0 are the c-axis lattice constant evaluated from Bragg's law (2dsinθ = nλ) and the c-axis lattice constant for strain free bulk ZnO, respectively. The parameter σ is the residual in-plane biaxial stress calculated from the out-of-plane stress.…”

ZnO QDs Deposited on Si by Sol-Gel Method: Role of Annealing Temperature on Structural and Optical Properties

“…The values of strain along the c-axis (ɛ zz ) are determined by using the following formula (Ghosh et al, 2004):…”

Unusual nonlinear strain dependence of valence-band splitting in ZnO

“…Strain can significantly modify the electronic band structures of a material [1][2][3], thus it can have strong effects on the structural, electrical and optical properties of the material [4][5][6]. Because of this, it has been extensive studied both theoretically and experimentally in the past decades and has often been used in designing electronic devices to enhance the device performance.…”

“…Because of this, it has been extensive studied both theoretically and experimentally in the past decades and has often been used in designing electronic devices to enhance the device performance. There are many different ways to apply strain, e.g., by applying external stress, having lattice and/or crystal structure mismatch between the epi-film and substrate [4] or between the layers in a heterostructure superlattice [7], or having reconstructions on a polar surface [8].…”