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Multilayer Zn50Sb50/Ge8Sb92 (ZS/GS) thin films were proposed and fabricated by alternate sputtering. The crystallization behaviors of nanocomposite ZS/GS thin films induced by heating were investigated by in situ resistance measurement. The crystallization behaviors of ZS/GS thin films can be regulated by tuning the thickness ratio and periods. The multilayer [ZS (8 nm)/GS (4 nm)]4 ([ZS(8)/GS(4)]4) thin film exhibits a high crystallization temperature (~ 245 °C), a large crystallization activation energy (2.61 eV), and high data retention ability (168 °C). The phase structure and thickness variation of the [ZS(8)/GS(4)]4 thin film were analyzed through x-ray diffraction (XRD) and x-ray reflection (XRR), respectively. The volume shrinkage during crystallization was as small as 3.9%. The multilayer structure and interface stability were confirmed by using transmission electron microscopy (TEM). A picosecond laser pump-probe system was used to evaluate the transition speed. The crystallization and amorphization periods of the [ZS(8)/GS(4)]4 thin film were only about 6.2 ns and 3.9 ns, respectively. [ABSTRACT FROM AUTHOR]

The influence of nitrogen dopant on the structure of the phase-change material Sb has been investigated by ab initio molecular dynamics simulations. The doped N exist as SbN complex in amorphous phase and would not enter into the rhombohedra phase of crystalline Sb. During crystallization of the amorphous phase, no N2 molecule is formed and part of the N–Sb bonds are broken to release Sb atoms which contribute to growth of crystal nuclei by forming more Sb–Sb bonds. Remaining N–Sb bonds would segregate at the grain boundaries and retard growth of crystal nuclei. [ABSTRACT FROM AUTHOR]

Superlattice-like Ge5Sb95/ZnSb (SLL GS/ZS) thin films were fabricated by radio-frequency magnetron sputtering technology. [GS(4 nm)/ZS(10 nm)]4 thin films display excellent thermal stability, and their crystallization temperature, activation energy, and 10-year data retention temperature are 253 °C, 3.78 eV and 157 °C, respectively, which are higher than traditional Ge2Sb2Te5 (GST) thin films. Slight fluctuation (3.5%) in thin film volume during phase transition process indicates good reliability. Ultrafast crystallization speed (9.2 ns) in the [GS(4 nm)/ZS(10 nm)]4 thin film was validated, which contributes to accomplish rapid storage of data in phase change memory cell. Moreover, phase change memory cells based on [GS(4 nm)/ZS(10 nm)]4 thin films can achieve reversible SET and RESET operations with 20 ns width pulse. [ABSTRACT FROM AUTHOR]

Ga–Cd–O (GCO) thin films with different Ga contents were fabricated based on a solution-processed method. The direct optical bandgap of GCO films is changed from 2.89 to 4.53 eV with the Ga-content from 30% to 100% and their relationship agrees well with a second-order equation. The Raman spectra of GCO are dominated by three main features: a relatively sharp peak at ~260 cm−1 and two broad features at ~405 and 949 cm−1, and their variations with the Ga-content are analyzed associated with their phonon mode assignment. Moreover, thin-film transistors using the GCO channels all exhibit n-type transistor characteristics and the evolution of their key electrical parameters with the Ga-content is well elucidated by the structural and morphological properties. A saturation field-effect mobility of 5.1 cm2 V−1 s−1, on/off current ratio of 2.1  ×  107, subthreshold slop of 0.83 V/dec, and threshold voltage of  −6.8 V were achieved by the 50% Ga-content device. [ABSTRACT FROM AUTHOR]

Superlattice-like Ge50Te50/Ge8Sb92 (SLL GT/GS) thin film was systematically investigated for multi-level storage and ultra-fast switching phase-change memory application. In situ resistance measurement indicates that SLL GT/GS thin film exhibits two distinct resistance steps with elevated temperature. The thermal stability of the amorphous state and intermediate state were evaluated with the Kissinger and Arrhenius plots. The phase-structure evolution revealed that the amorphous SLL GT/GS thin film crystallized into rhombohedral Sb phase first, then the rhombohedral GeTe phase. The microstructure, layered structure, and interface stability of SLL GT/GS thin film was confirmed by using transmission electron microscopy. The transition speed of crystallization and amorphization was measured by the picosecond laser pump-probe system. The volume variation during the crystallization was obtained from x-ray reflectivity. Phase-change memory (PCM) cells based on SLL GT/GS thin film were fabricated to verify the multi-level switching under an electrical pulse as short as 30 ns. These results illustrate that the SLL GT/GS thin film has great potentiality in high-density and high-speed PCM applications. [ABSTRACT FROM AUTHOR]

Phase-change memory has attracted enormous attention for its excellent properties as compared to flash memories due to their high speed, high density, better date retention and low power consumption. Here we present Sb7Te3/Ge multilayer films by using a magnetron sputtering method. The 10 years’ data retention temperature is significantly increased compared with pure Sb7Te3. When the annealing temperature is above 250 °C, the Sb7Te3/Ge multilayer thin films have better interface properties, which renders faster crystallization speed and high thermal stability. The decrease in density of ST/Ge multilayer films is only around 5%, which is very suitable for phase change materials. Moreover, the low RESET power benefits from high resistivity and better thermal stability in the PCM cells. This work demonstrates that the multilayer configuration thin films with tailored properties are beneficial for improving the stability and speed in phase change memory applications. [ABSTRACT FROM AUTHOR]

Multilayer SnSb4/ZnSb (SS/ZS) thin films have been investigated for phase change applications. The composition [SS (4 nm)/ZS (10 nm)]4 exhibits a high crystallization temperature (Tc ∼ 230 °C), high data retention temperature for 10 years (T10-yr ∼ 152 °C), small density change, and low thermal conductivity. A cell based on [SS (4 nm)/ZS (10 nm)]4 achieves fast SET/RESET switching speed (∼10 ns) and low reset power consumption (the energy for RESET operation = 9.6 × 10−13 J). [ABSTRACT FROM AUTHOR]

Effects of oxygen incorporation on the crystallization characteristics and crystal structure of Ge8Sb92 films were systematically investigated. The amorphous-to-crystalline transition was studied by in situ resistance measurement. The thermal stability, electrical resistance and band gap of Ge8Sb92 material increase significantly by the addition of oxygen. X-ray diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy illustrate that a small amount of oxygen dopant can inhibit the grain growth and limit the grain size because of the formation of Ge and Sb oxide. Atomic force microscopy and x-ray reflectivity results indicate that the film surface becomes smoother and the film thickness change becomes smaller after oxygen doping. Phase change memory cells based on oxygen-doped Ge8Sb92 film were fabricated to evaluate the electrical properties as well. All the results demonstrate that suitable incorporation of oxygen is an effective way to enhance the comprehensive performance of Ge8Sb92 thin films for phase change memory application. [ABSTRACT FROM AUTHOR]