Reproducible resistive‐switching behavior in copper‐nitride thin film prepared by plasma‐immersion ion implantation

Abstract

Copper nitride film prepared by plasma‐immersion ion implantation (PIII) is demonstrated to exhibit reversible resistance variance character. By forming a gradually distributed nitrogen concentration in the Cu‐nitride film, the nitride‐based memory devices show bipolar nature with a low operation voltage, forming‐free characteristics and a distinguishable resistance ratio. The bipolar switching behavior is attributed to the formation and rupture of conductive filaments within a cycle, which is confirmed by spreading‐resistance images of a conducting atomic force microscope. Based on X‐ray photoelectron spectroscopy (XPS) analysis, semiconducting Cu3N phase and metallic Cu4N phase coexist in the copper nitride film and local conducting filaments might be formed by interconnection of the metallic phases by migration of Cu+ ions under a bias voltage.

Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitrideCu3N

“…Copper nitride Cu 3 N is a relatively unexplored metastable semiconductor that has been studied for potential applications in write-once optical data storage [1][2][3], resistive random access memories [4], hybrid organic-inorganic solar cells [5], magnetic nanostructures, spin barrier tunnel junctions [6], and for rendering conductive dots and lines by maskless laser or electron-beam writing [7][8][9]. Applications may exploit the low decomposition temperature of ∼300…”

Influences of preparation methods on bipolar switching properties in copper nitride films

“…For Cu 2p peaks in Fig. 2a, there are no obvious position or shape differences between two kinds of samples, however, both of the Cu 2p peaks in two samples have a slight shift to higher energy compared to the pure Cu 2p peaks (951.9 eV and 932.2 eV) which could be attributed to the Cu\N bonding [16,18]. To further clarify this, N 1s peaks are shown in Fig.…”

“…According to the typical I-V curve and Lu et al's previous work [16], the resistive switching mechanism of Ni/Cu x N/Cu RRAM device are most likely to be the formation and rupture of Cu conducting filaments due to the high mobility of Cu ion and the vacancy in the body center of copper nitride crystal which provides Cu conducing filaments an easy access to grow through the Cu x N film. Thus, the switching mechanism of Ni/Cu x N/Cu RRAM system could be described as followed, the Cu ions from the bottom Cu electrode reach the top electrode through the grain boundaries in the film under the electrical field at the initial time, after that, they are reduced into Cu atoms which lead to the growth and random formation of conducting filaments throughout the Cu x N film and turn the RRAM cell into LRS, thus, a high current could flow through the Cu conducting filaments, however, when the opposite bias is applied, the Cu atoms in the film are anodized into Cu ions again near the anode, which lead to the rupture of the conducting filaments and turn the LRS back to HRS.…”

“…Copper nitride film was formed by implanting N+ion into the top copper layer by a PIII system (PIII-Cu x N film) at a room temperature with progressively increased negative high voltage from 2 to 10 kV at nitrogen working pressure of 0.8 Pa and radio frequency power of 70 W, so as to control the total nitrogen concentration accurately and to form a gradually increasing nitrogen concentration from the bottom to the top in the Cu x N film. The total implant dose was estimated about 4.1×10 16 cm −2 and the implantation depth was theoretically simulated to be about 45 nm. The film made by RMS (RMS-Cu x N film) was grown on the Cu/TaN/SiO 2 /Si substrate by using a copper target with a purity of 99.9% at a room temperature.…”

“…Most recently, Lu et al [16] firstly reported that the copper nitride films prepared by PIII with implantation voltage gradually up to 15 kV could show reversible resistance variance character. However, this Cu x N based RRAM device only provided an endurance of about 50 with an acceptable resistance window of about 10 times.…”