Ultrafast phase change and long durability of BN-incorporated GeSbTe

Abstract

BN-incorporated amorphous Ge 2 Sb 2 Te 5 (GST) films were deposited by an ion beam sputtering deposition (IBSD) method using GST and BN targets. Based on in situ sheet resistance measurements, we confirmed that as the amount of BN increased, the crystallization temperature (T c ) increased from 150 o C to 260 o C. It was demonstrated that the phase change speed of BN-incorporated GST is ten times faster than that of GST using a nanosecond laser.By evaluating Johnson-Mehl-Avrami (JMA) plots and scanning electron microscope (SEM) images, it was confirmed that the one-dimensional grain growth is dominant during the fast phase change of BN-incorporated GST because BN impurities can act like nuclei during the initial stage of crystal growth. After the 100 iteration test under rigorous acceleration conditions of SET/RESET switching using the pulsed laser system, it was confirmed that the void formation and thickness variation are very limited in the BN-incorporated GST, as compared to GST. This result originates from the low phase change stress of the BN-incorporated GST films during one-dimensional growth. The electrical SET speed and cyclability of the BNincorporated GST device also improved significantly compared to GST.

Effect of Electrode Material on the Crystallization of GeTe Grown by Atomic Layer Deposition for Phase Change Random Access Memory

“…are the values of resistance in the fully amorphous and crystalline phases. The JMA kinetics is an equation for kinetics in the phase transition mechanism, generally expressed as shown in Equation (2) [21,22]. xfalse(tfalse)=1−expfalse[−false(ktfalse)nfalse] where n is the Avrami coefficient and k is the effective rate constant.…”

“…xfalse(tfalse)=1−expfalse[−false(ktfalse)nfalse] where n is the Avrami coefficient and k is the effective rate constant. Equation (2) can be modified to deal with the R–t curve, as follows: [21,22,23] lnfalse[lnfalse[11−xfalse(tfalse)false]false]=nlnt+nlnk…”

“…According to Equation (3), n can be acquired from the slope of ln(t) versus ln[−ln(1− x (t))] plot. The Avrami coefficient, n , can be expressed as the sum of two elements, n = a + b , where a indicates the nucleation index, b indicates the dimensionality of the growth (such as b = 1, 2, or 3 for one-, two-, or three-dimensional growth, respectively, where nuclei grow like needles, disks, or spheres) [21,22,23,24,25].…”

Suppression for an intermediate phase in ZnSb films by NiO-doping

“…The mean n value (0.44) of the (ZnSb) 96 (NiO) 4 is much smaller than that of ZnSb (1.12), indicating that the incubation period for crystallization is relatively short. The decrease of the Avrami exponent (n) indicates that the phase transition is likely to be heterogeneous 25 , because the dispersed NiO particles provide additional nucleation sites. These nuclei can accelerate the crystalline growth in an ultrafast one-dimensional mode.

Figure 7Results taken from ZnSb film using the of ( a ) R–T curves at different heating rates, ( b ) curves showing fraction of crystallization at different heating rates, ( c ) Ozawa’s plot, and ( d ) temperature-dependent kinetic exponents.

Figure 8Results taken from (ZnSb) 96 (NiO) 4 film using the of ( a ) R–T curves at different heating rates, ( b ) curves showing fraction of crystallization at different heating rates, ( c ) Ozawa’s plot, and ( d ) temperature-dependent kinetic exponents.

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Controllable crystal growth and fast reversible crystallization-to-amorphization in Sb2Te-TiO2 films

“…In this plot, n is the slope of ln(t) versus ln[-ln(1-χ(t))] plot. Although the JMA plot characterizes the isothermal crystallization on the minute time scale, it is also possible to subtract the n from the nanosecond time scale according to previous reports 33 34 . As shown in Fig.…”