ZnO-porous silicon nanocomposite for possible memristive device fabrication
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ZnO-porous silicon nanocomposite for possible memristive device fabrication Lizeth Martínez, Oscar Ocampo, Yogesh Kumar and Vivechana Agarwal*
Abstract Preliminary results on the fabrication of a memristive device made of zinc oxide (ZnO) over a mesoporous silicon substrate have been reported. Porous silicon (PS) substrate is employed as a template to increase the formation of oxygen vacancies in the ZnO layer and promote suitable grain size conditions for memristance. Morphological and optical properties are investigated using scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. The proposed device exhibits a zero-crossing pinched hysteresis current-voltage (I-V) curve characteristic of memristive systems. Keywords: Memristor; Zinc oxide; Porous silicon; Composite; Nanocrystallites
Background The memristor, known as the fourth fundamental circuit element, is a device whose main characteristic is the dependance of resistance according to the flux of charge passing through it and has the ability to remember its last resistance state. It was hypothesized by Chua [1] in 1971, but it was not until 2008 that it was first fabricated at HP Labs [2]. Since then, the fabrication and study of memristive devices have become very popular due to their applications in information storage, non-volatile memories, neural networks, etc. [3-5] Memristive switching behavior has been observed in many metal oxides [6,7] and attributed to the migration of oxygen vacancies within the oxide layers and grain boundaries [8,9], but still, transport mechanisms are being studied and different models have been suggested [7-9]. Zinc oxide (ZnO) possesses several interesting properties and has been extensively studied for its technological applications, specifically in electronic and optoelectronic devices such as photodetectors [10,11], light-emitting diodes [12], solar cells [13,14], and gas sensing [15]. On the other hand, porous silicon (PS)-ZnO composites have been used for white light emission [16] and to tune ZnO grain size for possible sensing applications [17]. This leads to the possibility to fabricate a tunable memristive device made of ZnO deposited on a PS template for optimizing the conditions of grain size, * Correspondence: vagarwal @uaem.mx Center for Engineering and Applied Sciences (CIICAp-UAEM), Av. Universidad 1001. Col. Chamilpa, Cuernavaca, Morelos 62209, Mexico
oxygen vacancies, defects, etc. to achieve tunable response from the device. The memristive behavior is demonstrated and explained through scanning electron microscopy (SEM) and photoluminescence (PL) characterization. The effect of annealing on morphology and photoluminescence response is also studied.
Methods PS samples were obtained by wet electrochemical etching using p++-type (100) Si wafers with a resistivity of 0.002 to 0.005 Ω cm. The anodization process was carried out using an electrolyte solution composed of hydrofluoric acid (48 wt% HF) and ethanol (99.9 %) in a volumetric ratio of 1:1. The bilayer porous
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