Effect of Morphological Change on Unipolar and Bipolar Switching Characteristics in Pr 0.7 Ca 0.3 MnO 3 Based RRAM
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Effect of Morphological Change on Unipolar and Bipolar Switching Characteristics in Pr0.7Ca0.3MnO3 Based RRAM Neeraj Panwar1, Pankaj Kumbhare1, Ajit K. Singh2, N. Venkataramani2 and Udayan Ganguly1 1 Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India 2 Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India ABSTRACT We have demonstrated that pulsed laser deposition (PLD) conditions, i.e. O2 partial pressure (pO2) and temperature (T), enable control over the polarity of resistance switching in PCMO (Pr0.7C0.3MnO3) i.e. unipolar resistive switching (URS) vs. bipolar resistive switching (BRS). We observe by detailed physical characterization that BRS occurs in poly-crystalline thin films while URS is seen in amorphous films – indicating the materials origin of URS vis-a-vis BRS. BRS shows attractive lower voltage operation, no forming and lower variability than URS. INTRODUCTION Bipolar RRAM (Resistive Random Access Memory) has various attractive properties like low power and current required for resistance switching [1]. Although TMO (Transition Metal Oxides) e.g. HfO2, ZrO2 etc.) based RRAM have shown excellent switching, but their mechanism of filamentary conduction has two challenges. First, filament formation (or forming process) needs higher current and voltage in the first programming cycle than during regular operation (set, reset and read) which produces additional requirement on selector device, array and peripheral circuits [2]. Second, the TMO based RRAM have high variability from the probabilities of single filament dependent process [3]. In contrast, manganite based RRAM exhibit area scalable interface type resistive switching– which is forming-less [4-5]. BRS has been explored extensively in PCMO with reactive top electrode [4-7]. Unipolar PCMO RRAM has been demonstrated recently [8-10]. We have recently reported control of URS vs. BRS in PCMO, based on the PLD process conditions i.e. pO2 and T, based on DC sweep. Low thermal budget based BRS was also demonstrated by RTA (Rapid Thermal Anneal) of room temperature deposited samples [8]. However, materials origin of URS vs. BRS needs to be investigated. In addition to the nominal DC performance is presented earlier, variability and the memory performance (speed, endurance etc.) needs to be evaluated. In this paper, we compare the DC memory switching performance of URS to BRS to highlight the major differences including power requirement, forming and variability. We identify the differences in the thin film morphology between BRS and URS films based on physical characterization. Finally, we present pulse based electrical characterization to evaluate memory performance (switching speed and endurance) of bipolar sample to demonstrate stateof-the-art bipolar RRAM performance in PCMO films.
EXPERIIMENTAL DETAILS The device d fabriccation was performed on n silicon waffers which w were cleaned by 2% HF ddip
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