Perpustakaan Digital ITB

Structural and morphological modifications have been performed on nanostructured ZnO thin films to obtain optimal optical, electrical and magnetic parameters. In this study, ZnO-based materials were grown by sputtering method. The nanostructured ZnO thin films were grown by using a starting material of ZnO powder and further grown on a silicon substrate (100) with a substrate temperature of 300 °C. As the comparison, nanostructured ZnO was also grown by spray method using Zn(CH3COO)2.H2O solution at the same substrate temperature of 300 °C. Sample characterizations were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), RT66A ferroelectric test, photoluminescence (PL), UV-Vis spectrophotometer, and magnetic properties measurement system (MPMS). From both methods, ZnO nanomaterials have been successfully fabricated. Based on initial characterization using XRD and FESEM, sputtered-ZnO nanomaterials have better structural and morphological characteristics, particularly in the distribution and uniformity of particle size. The sputtered-ZnO has a high orientation in the (002) plane whereas the sprayed-ZnO has dominant orientation in the (100), (002), and (101) planes. Furthermore, ZnO with sputtering method was preferred and became the focus of this study due to its high orientation in the polar plane. Further research focused on optimizing ZnO structures through variation of growth parameters (time and growth power) to obtain a uniform distribution and high strain. From the optimization process, it was found that the grain size of ZnO increases from 70.478 nm to 175.431 nm as the increase of deposition time, while the increase in deposition power up to 12W caused an increase of ZnO diffusion on the Si substrate so that it was arranged densely and has the uniform grain size of 55.768 nm. However, the XRD results show that ZnO with a denser and uniform arrangement has a small strain value. To obtain two conditions simultaneously, ie high strain values and uniform distribution, further research was conducted to modify the structure and morphology of ZnO. At this step, the ZnO structure was modified from nanoparticles to columnar. Here, the growth of the columnar structure can be performed at one stage by controlling the deposition parameters without any catalyst and patterning. Further modifications were performed with ii annealing and doping. It can be shown that the increase in annealing temperature led to the structural evolution of ZnO. All samples showed a wurtzite structure with a dominant crystal orientation in the (002) plane. A football-like polarization response showed a leakage current in the samples due to the presence of VO defects. Furthermore, the influence of structural modification on electronic properties has been observed. The decrease in sample size led a blue shift in the band gap where the electronic transition depends on the presence of defects in the system. Here, the carbon doping into ZnO caused a reduction in the columnar height and did not change the ZnO shape significantly. The addition of carbon atoms led a change in the polarization response and decrease of the leakage current. In addition, the presence of carbon atoms caused a red shift in the band gap. Furthermore, investigation of polarization properties in illuminated conditions indicated a change in polarization response in all the samples. The polarization curve shift was observed on the sample set of carbon-doped ZnO. Furthermore, the ferromagnetic response was obtained by modifying the structure of undoped ZnO NC. The presence of VO and VZn plays an important role in generating ferroelectric and ferromagnetic properties in the ZnO. The emergence of ferroelectric and ferromagnetic properties can be used to produce magnetoelectric properties, which are important keys in switchable and nonvolatile memory applications. Our results provide a good understanding about modification of optical, electronic and magnetic properties, which play an important role in the development of devices with high sensitivity, such as sensor and optoelectronic devices.