Instability of nitrogen doped Sb2Te3 for phase change memory application

Abstract

National Integrate Circuit Research Program of China [2009ZX02023-003]; National Basic Research Program of China [2007CB935400, 2010CB934300, 2011CB309602, 2011CB932800]; National Natural Science Foundation of China [60906004, 60906003, 61006087, 61076121By means of experimental methods and ab initio total energy calculations, we have studied the stability and properties of nitrogen doped Sb2Te3 (NST). The NST film displayed a higher crystallization temperature and sheet resistance than undoped Sb2Te3 (ST) film. Nevertheless, the sheet resistance of the crystalline NST film unexpectedly increased as the temperature increased when the temperature was above 260 degrees C. The X-ray photoelectron spectroscopy (XPS) showed that the nitrogen concentration and the Sb-N bonds were decreasing as the annealing temperature increased, and no nitrogen existed in the NST when annealed at 300 degrees C for 5 min. Our theoretical calculations showed that the incorporation of nitrogen into crystalline Sb2Te3 was not energetically favorable, and the nitrogen atoms preferred forming chemical bonds with Sb atoms to Te atoms. (C) 2011 American Institute of Physics. [doi:10.1063/1.3660705

Simulation of Phase‐Change‐Memory and Thermoelectric Materials using Machine‐Learned Interatomic Potentials: Sb2Te3

“…[ 21 ] In addition, the relatively low electrical resistivity of Sb 2 Te 3 , compared with that of GST, leads to large RESET currents and, hence, high switching power. [ 21,22 ] Doping with various elements has, therefore, also been used to try to improve the performance of Sb 2 Te 3 , including dopants, such as C, [ 23 ] N, [ 20 ] O, [ 24 ] Al, [ 25 ] Si, [ 26 ] Ti, [ 27 ] Cr, [ 28 ] Zn, [ 29 ] Ge, [ 30 ] Ag, [ 31 ] Y, [ 32 ] and Sc. [ 33 ] Very recently, a nano‐engineered hetero‐structure, consisting of alternating layers of a few nanometers (3–5 nm) of Sb 2 Te 3 and TiTe 2 , has been shown to exhibit much‐improved PCM behavior, particularly relating to a reduction in time‐dependent resistance “drift” and in electrical noise in the glassy state of the PCM material, Sb 2 Te 3 .…”

“…[19] Sb 2 Te 3 also has a very high crystallization speed and, therefore, is a potential candidate material to surpass the data-rate limit imposed by the rate-limiting crystallization process of other PCM materials. [20] However, it also has a low crystallization temperature and, hence, poor thermal stability of the amorphous phase, which is, therefore, detrimental to data retention in the glassy state ("0") at high operating temperatures. [21] In addition, the relatively low electrical resistivity of Sb 2 Te 3 , compared with that of GST, leads to large RESET currents and, hence, high switching power.…”

Toward Single‐Cell Multiple‐Strategy Processing Shift Register Powered by Phase‐Change Memory Materials

“…Experiments have demonstrated that incorporating nitrogen into the PCM is an efficient way to improve the data retention/stability of amorphous states by hindering crystallization. [ 42 ] A similar type of material was utilized in this work, which indicates that our strategies are similar. After setting the initial state of the cell to the amorphous state, a specified M state is created in the doped active layer using a stimulus (Figure S3, Supporting Information).…”

Origin of the concentration-dependent effects of N on the stability and electrical resistivity in polycrystalline Ge1Sb2Te4

“…The data show that the formation energy is broadly positive, which means that the incorporation of N is not easy at 0 K, while in practice, this energy might be compensated in the non-equilibrium process with the participation of high energy nitrogen and GST target during the sputtering. 46 In Fig. 2(k), the formation energy of interstitial and vacancy site nitrogen exhibits an overall linear relationship with the doping concentration, indicating that in these configurations N will not interact with each other.…”

“…Since the thermal stability of N-dopants has been a concerning topic for nitrogen-doping, 9,46,49 the mean-square displacement (MSD) for nitrogen atoms in various nitrogen-doped polycrystalline cells at different doping levels was calculated, and is shown in Fig. 6.…”