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

Abstract

The structural evolution and phase-change kinetics of NiO-doped ZnSb films are investigated. NiO-doped ZnSb films exhibit a single-step crystallization process, which is different from that of undoped ZnSb. NiO-doped ZnSb can directly crystallize into a stable ZnSb phase at temperatures greater than 320 °C with suppression of a metastable ZnSb phase. These characteristics enlarge the amorphous/crystalline resistance ratio by approximately five orders of magnitude. Moreover, NiO doping of ZnSb films increases crystallization temperature from 260 to 275 °C, improves data retention temperature from 201.7 to 217.3 °C and increases crystalline activation energy from 5.64 to 6.34 eV. The improvement of the thermal parameters in the nanocomposite can be attributed to stable ZnSb grain growth refinement owing to the dispersion of NiO particles in the sample matrix. This provides additional nucleation sites and produces more ZnSb/NiO interfaces, which can initiate the nucleation and accelerate crystallization. The kinetic exponent n decreases from 1.12 to 0.44, which confirms the ultrafast one-dimensional growth and heterogeneous phase transition of the NiO-doped ZnSb films. The improved thermal stability, larger resistance ratio and direct transition to a stable phase with ultrafast one-dimensional crystal growth indicate the good potential of these materials in phase-change memory applications.

Self-Limited Growth of Nanocrystals in Structural Heterogeneous Phase-Change Materials during the Heating Process

“…As for the samples annealed at 350 °C, the ZnSb-Al 2 O 3 films exhibit three vibration peaks marked as C, D, and E, which are located at ∼112, ∼149, and ∼170 cm –1 , respectively. It is in good agreement with the vibration peaks in pure ZnSb annealed at 350 °C, implying that the Raman peaks are ascribed to the vibration of the stable ZnSb phase . However, the intensity of Raman peaks was slightly increased, while for ZnO-doped ZnSb films, the three typical Raman peaks’ intensity becomes gradually weaker with higher ZnO-doping concentration, illustrating that the evolution of Raman peaks may be influenced by the compression stress .…”

“…It is in good agreement with the vibration peaks in pure ZnSb annealed at 350 °C, implying that the Raman peaks are ascribed to the vibration of the stable ZnSb phase. 14 However, the intensity of Raman peaks was slightly increased, while for ZnO-doped ZnSb films, the three typical Raman peaks' intensity becomes gradually weaker with higher ZnO-doping concentration, illustrating that the evolution of Raman peaks may be influenced by the compression stress. 15 The compression is originated from the interface between ZnSb domain boundaries and the separated oxides.…”

“…All the as-deposited and 250 °C-annealed films exhibit a wide broadening peak located at ∼155 cm –1 , implying the amorphous state. Increasing the annealing temperature to 300 °C, the Raman spectra of pure and Al 2 O 3 -doped ZnSb films exhibit two peaks A and B located at ∼113 and ∼150 cm –1 , which are ascribed to the vibration of the metastable ZnSb phase . The locations of two Raman peaks remain unchanged, but the intensity of Raman peaks becomes obviously stronger, implying that the addition of Al 2 O 3 fails to control the growth of ZnSb grains.…”

“…Increasing the annealing temperature to 300 °C, the Raman spectra of pure and Al 2 O 3 -doped ZnSb films exhibit two peaks A and B located at ∼113 and ∼150 cm −1 , which are ascribed to the vibration of the metastable ZnSb phase. 14 The locations of two Raman peaks remain unchanged, but the intensity of Raman peaks becomes obviously stronger, implying that the addition of Al 2 O 3 fails to control the growth of ZnSb grains. For ZnOdoped ZnSb films, they exhibit similar Raman peaks as that observed in pure ZnSb when the ZnO-doping concentration is less than 12.3 atom %, but they show a broadening peak when the doping concentration increases to 15.1 and 18.2 atom %, indicating the amorphous state.…”

Investigation of laser-irradiated structure evolution and surface modification by in situ Micro-Raman spectroscopy

“…The two peaks shift towards a low wavenumber at 140.6 cm -1 and 104.3 cm -1 at 500 mW, respectively. Comparing the peak positions with that in the Raman spectra for thermal-annealed ZnSb samples [11], we confirm that the Raman peaks attribution roughly coincides with the precipitation metastable ZnSb phases.…”