Nitrogen Doping Effect on Phase Change Optical Disks

Abstract

The nitrogen doping effect on the Ge–Sb–Te recording layer was quantitatively examined. We succeeded in the quantitative analysis of the nitrogen concentration in the Ge–Sb–Te–(N) recording layer by secondary ion mass spectrometry (SIMS) observation. The nitrogen concentration could be finely controlled at a high deposition rate of 4.7 nm/s. The addition of a small amount of nitrogen remarkably improved the overwrite cycle numbers. We found that the most suitable nitrogen concentration was from 2 to 3 at%. We proposed a model to explain the nitrogen atom function in the recording layer. The nitrogen atoms produced nitrides, which are condensed near the grain boundaries of Ge–Sb–Te microcrystals. This resulted in the formation of very thin wrappings, which wrap the crystal grain in a manner similar to that of the peel of a peach and suppressed the micro-material flow. We achieved 8×105 overwrite cycles at λ=790 nm, N A=0.50 and using the pit position modulation (PPM) recording method where the minimum bit length is 0.87 µm.

Ion Implantation in Phase Change Ge2Sb2Te5 Thin Films for Non Volatile Memory Applications

“…The increase of the crystallization temperature in oxygen (Jeong et al, 2001) and nitrogen [Kojima et al, 1998, Jeong et al, 2000 doped GST has been already reported in literature, as well as the reduction of the grain size in samples containing nitrogen. Several models have been proposed (Jeong et al, 2001, Jeong et al, 2000 trying to simultaneously explaining the effect of both O and N in order to find the optimal dopant to engineer specific properties of GST.…”

“…In fact, it has been shown that nitrogen doping during deposition (Kojima et al 1998, Jeong et al 2000 increases the amorphous stability and reduces the grain size, improving the cell cyclability.…”

“…First, it has been observed that the reduced grain size could be caused by dopant segregation near grain boundaries in the form of nitrides (Kojima et al, 1998). The resistance of the crystalline phase would increase due to additional electron scattering from grain boundaries (Horii et al, 2003).…”

Origin, secret, and application of the ideal phase‐change material GeSbTe

“…It is apparent respectively in the left-and right-hand triangles that T x is far higher than room temperature and t cry is sufficiently short, <50 ns. By the environmental acceleration tests on the real optical disk device using the Arrhenius method, the estimated lifetime of the amorphous marks formed in the crystalline GeSbTe was more than several tens of years at room conditions (308C, 80% RH) [10]. It is amazing that the ratio between the estimated lifetime (30 years) and the laser crystallization time (30 ns) reaches 10 [17][18] .…”

Improvement of reliability and speed of phase change memory devices with N7.9(Ge46.9Bi7.2Te45.9) films

“…Nitrogen doping was utilized to increase the temperature of crystalline in the film. [16][17][18][19][20] After fabricating PCM devices with island cells of 200 nm in diameter, the electrical properties of the devices were evaluated in terms of the characteristics of the material, compared with corresponding findings for 7 at% nitrogen doped Ge 2 Sb 2 Te 5 materials. The optimum composition of GeBiTe film together with nitrogen incorporation resulted in the production of a potentially promising phase change material for use in high performance PCM and forthcoming SCM applications.…”