Reliable resistive switching of epitaxial single crystalline cubic Y-HfO₂ RRAMs with Si as bottom electrodes

Abstract

Previous studies have mainly focused on the resistive switching (RS) of amorphous or polycrystalline HfO2-RRAM. The RS of single crystalline HfO2 films has been rarely reported. Yttrium doped HfO2 (YDH) thin films were fabricated and successful Y incorporation into HfO2 was confirmed by x-ray photoemission spectroscopy. A pure cubic phase of YDH and an abrupt YDH/Si interface were obtained and verified by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. A Pt/YDH/n++-Si heterostructure using Si as the bottom electrode was fabricated, which shows stable RS with an ON/OFF ratio of 100 and a reliable data retention (104 s). The electron transport mechanism was investigated in detail. It indicates that hopping conduction is dominating when the device is at a high resistance state, while space charge limited conduction acts as the dominant factor at a low resistance state. Such behavior, which is different from devices using TiN or Ti as electrodes, was attributed to the Y doping and specific YDH/Si interface. Our results demonstrate a proof of concept study to use highly doped Si as bottom electrodes along with single crystalline YDH as insulator layer for such RRAM applications as wireless sensors and synaptic simulation.

In-Gap States of HfO2 Nanoislands Driven by Crystal Nucleation: Implications for Resistive Random-Access Memory Devices

“…8,9 The formation of oxygen vacancies is affected by the crystallinity of the film, as well as by doping of HfO 2 with other transition metal ions. 10 Different resistive switching properties are observed in amorphous and polycrystalline films where grain boundaries can serve as conductive pathways, owing to the high density of oxygen vacancies at these locations. 11 It is essential for the improvement of nanosized hafnia-based ReRAM devices to understand in detail the nature of surface and defect states which are located at the surface of HfO 2 -based thin films and grain boundaries, leading to the distinctly enhanced conductivity.…”

“…Resistive random-access memory (ReRAM) devices based on HfO 2 show great promise for next-generation non-volatile memories owing to their potential for high speed, low power consumption, and ultimate scalability. HfO 2 ReRAM devices belong to the valence change mechanism (VCM) type, which is based on the resistive hysteresis driven by oxygen vacancy drift and the resulting redox reactions. , The formation of oxygen vacancies is affected by the crystallinity of the film, as well as by doping of HfO 2 with other transition metal ions . Different resistive switching properties are observed in amorphous and polycrystalline films where grain boundaries can serve as conductive pathways, owing to the high density of oxygen vacancies at these locations .…”

Effect of Bias Voltage on Substrate for the Structure and Electrical Properties of Y:HfO2 Thin Films Deposited by Reactive Magnetron Co‐Sputtering

“…[ 30 ] The O 1s peak at 532.2 eV can be attributed to the oxygen vacancies. [ 31,32 ] The results confirm the existence of oxygen vacancies in Y:HfO 2 films, which may be caused by metal Hf, [ 33 ] doping Y, [ 33 ] and annealing process in nitrogen atmosphere. [ 34 ] In addition, the Y 3d 5/2 and Y 3d 3/2 doublet peaks are observed at 156.8 and 158.8 eV and shown in Figure 1c.…”

Refined analysis of C–V and I–V characteristics of Al/dielectric/Si structures containing nanosized Ta2O5/SiOxNy dielectric stack

“…In principle, this is the same expression as (6) with the index q omitted for simplicity, and compatibility with expressions from other works on leakage currents.…”

“…The correct determination of their electrical and dielectric properties requires the attentive use of various methods. Both the bulk properties and the interface with semiconductor substrate are important [6,7]. In particular, the determination of the distribution of interface states density over the semiconductor bandgap faces significant problems when downscaling dielectric layers of the devices in the nanoscale.…”