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  • 學位論文

苝四甲酸二酐有機自旋閥受成長溫度以及退火溫度的影響

The effects of growth and annealing temperature on the magnetoresistance in PTCDA-based spin valves

指導教授 : 林敏聰
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摘要


我們嘗試製作苝四甲酸二酐(PTCDA) 的有機自旋閥並研究磁阻 (Magnetoresistance)、載子飄移率(Mobility)以及晶體結構間的關係。由於在元件製作上加熱處理的情況是非常常見的,因此我們嘗試了解溫度這個參數的影響。 在過去文獻中指出成長溫度(Growth temperature)以及退火溫度(Anneal temperature)會影響PTCDA 的排列情況,而有序排列的有機半導體其載子飄移率會比非結晶的情況高出數個數量級,我們透過改變溫度提高PTCDA 的有序性並藉此希望提高材料的自旋擴散長度(Spin diffusion length)以得到較佳的磁阻效應。在改變成長溫度方面我們改變七種不同的成長溫度(攝氏100 度,130, 150, 180, 200, 230, 以及 250 度)並且使用X 光繞射以觀察其晶體排列情形,發現晶體大小隨著成長溫度增加有變大的趨勢。接著利用四點量測測量其磁阻以及載子飄移率以研究材料排列情況對電性的影響。MR 隨著成長溫度的增加有先降低再爬升的趨勢,而我們尚不了解載子飄移率與成長溫度間的關係。在改變退火溫度的情況下,先在室溫下製作出自旋閥接著分別做了五組不同退火溫度(攝氏100 度, 130, 150, 180 以及 200 度)。同樣的,我們測量X 光繞射、磁阻和載子飄移率以觀察它們之間的關係。我們發現MR隨著退火溫度增加逐漸下降,同時晶體大小以及載子飄移率也都隨著降低。

並列摘要


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.

參考文獻


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