| Summary: | 碩士 === 臺灣大學 === 物理研究所 === 98 === The relation between spin dependent transport and crystalline structure of organic material perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) has been studied. The fabrication of semiconductor devices often encounter thermal treatment processes, which may affect the properties of the material and cause problems. According to previous studies, the growth temperature and anneal temperature will influence the structure of PTCDA, therefore we attempt to realize the influence of temperature for the PTCDA junctions. Also, the crystal structure will influence the carrier mobility and hence change the spin diffusion length, which is an important indication in spintronics applications.
We fabricated //NiFe/CoFe/AlOx/PTCDA/CoFe organic spin valves (OSVs) with the variation of growth temperatures (100℃, 130 ℃, 150 ℃, 180 ℃, 200 ℃, 230 ℃, and 250 ℃) and set up the four-probe measurement in current perpendicular to plane (CPP) configuration to characterize their electrical properties such as magnetoresistance (MR) and mobility. We discovered that the MR ratio first decreases with the growth temperature but then increases above 150 ℃. We also studied the annealing effect in the organic spin valve system with five different annealing temperatures (100℃, 130℃, 150℃, 180℃ and 200℃). The MR ratio decrease and the resistance increase with the annealing temperature.
Furthermore, we deposit the PTCDA on //NiFe/CoFe/AlOx in the same growth temperatures and annealing temperatures, and then check their structure by X-ray diffraction (XRD) technique. The crystal size could be fitted by the full width half maximum (FWHM) of PTCDA (102) peak.
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