Effects of embedding Au layer on the resistive switching characteristics of NiO memory devices

• Main Authors: Yung-SungLin, 林永崧
• Other Authors: Jen-Sue Chen
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/04981670917424214367

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 98 === In this research, nickel oxide(NiO) thin films were deposited by reactive sputtering from nickel(Ni) target. Resistance random access memory(RRAM) devices were fabricated using NiO film without embedded Au layer(Al/NiO/Pt), NiO film without embedded Au layer after thermal treatment in oxygen ambient(Al/anneal_NiO/Pt), and NiO film with embedded Au layer(Al/NiO/Au/NiO/Pt). The mechanism of resistive switching is explored based on the current-voltage(I-V) and capacitance-voltage(C-V) measurements of the devices, in combination with material characterization by atomic force microscopy(AFM) and transmission electron microscopy(TEM). Thickness and micro-structure of NiO films and embedded Au layer were analyzed by using transmission electron microscopy. Rutherford Backscattering Spectrometry(RBS) and Electron Probe X-ray Microanalyzer (EPMA) were utilized to determine the composition of NiO films. The crystal structure of NiO films was identified by grazing incident angle X-ray diffraction (GIAXRD). Mobility, carrier concentration and resistivity of NiO films were determined by Hall measurement. Film resistivity of NiO films was also determined by four-point probe. The electrical properties of RRAM devices were measured by precision semiconductor parameter analyzer (Agilent 4156C) and LCR meter (Agilent 4284A). Finally, atomic force microscopy was utilized to analyze local conductivity of NiO films. Experimental results reveal that all NiO films, before and after thermal treatment, are polycrystalline. The O/Ni atomic ratios are larger than 1, and the NiO is a P-type semiconductor. After thermal treatment at 500oC in oxygen ambient, the O/Ni atomic ratio approaches to 1. Carrier concentration is decreased, and the resistivity and mobility are increased. Resistive switching phenomenon can be seen in all RRAM devices. Nevertheless, the device yield of resistive switching is greater for the devices without thermal treatment than the devices with thermal treatment. Switching voltage values as well as the standard deviation are both reduced for devices with embedded Au layer. In addition, current stress test indicates that the on-state and off-state maintain stable for at least 3600 seconds. The I-V conduction mechanism of all structures is ohmic at on-state, and that of all structures is Schottky emission at off-state. RRAM devices of NiO films without and with embedded Au layer were also measured C-V curves. A distinct peak is seen in the C-V curves of all devices and the peak is larger for the device at on-state than at off-state, and it is larger for NiO with embedded Au layer than NiO without embedded Au layer. The C-V curves suggest that the number of charges in NiO is greater at on-state than at off-state. Moreover, the number of charges in NiO films increases when embedding an Au layer.