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The potentials of Sn, In, or Al doped ZnSb thin film as candidates for phase change materials have been studied in this paper. It was found that the Zn-Sb bonds were broken by the addition of the dopants and homopolar Zn-Zn bonds and other heteropolar bonds, such as Sn-Sb, In-Sb, and Al-Sb, were subsequently formed. The existence of homopolar Sn-Sn and In-In bonds in Zn₅₀Sb₃₆Sn₁₄ and Zn₄₁Sb₃₆In₂₃ films, but no any Al-Al bonds in Zn₃₅Sb₃₀Al₃₅ film, was confirmed. All these three amorphous films crystallize with the appearance of crystalline rhombohedral Sb phase, and Zn₃₅Sb₃₅Al₃₅ film even exhibits a second crystallization process where the crystalline AlSb phase is separated out. The Zn₃₅Sb₃₀Al₃₅ film exhibits a reversible phase change behavior with a larger Ea ( 4.7 eV), higher Tc (~ 245ᴼ C), better 10-yr data retention (~ 182ᴼ C), less incubation time (20 ns at 70 mW), and faster complete crystallization speed (45 ns at 70 mW). Moreover, Zn₃₅Sb₃₀Al₃₅ film shows the smaller root-mean-square (1.654 nm) and less change of the thickness between amorphous and crystalline state (7.5%), which are in favor of improving the reliability of phase change memory.

We explored the structural and physical properties of Sb-rich Zn-Sb-Te films in order to combine the good thermal stability of ZnSb with the high crystallization speed of Sb2Te. The films generally exhibit two different crystallization characteristics described as follows: amorphous → Sb2Te crystalline phase if the Zn content in the film is less than ∼10 at. % and amorphous → Sb crystalline phase if the Zn content is more than ∼10 at. %. Among the films, the Zn28.62Sb53.69Te17.69 film was found to show the highest crystallization temperature (∼255°C), best 10 year data retention (∼165.9°C), and shortest crystallization time of ∼58 ns at 70 mW with a stable rhombohedral Sb phase; thus, it is considered promising for phase-change memory applications.

We prepared Mg-doped Sb2Te films and investigated their structural, optical and electrical properties. It was found that Mg doping can increase the crystallization temperature, suppress the crystal growth and shorten the crystallization time of Sb2Te. Compared to Ge 2Sb2Te5, the optimal composition of Mg 21.5(Sb2Te)78.5 exhibited a higher crystallization temperature (~183 °C), larger crystallization activation energy (~3.86 eV), and better data retention ability (maintaining the amorphous state at ~121 °C for ten years), indicating improved amorphous state stability due to the formation of Mg-Sb bonds. A reversible, repetitive optical switching behavior was realized in the Mg21.5(Sb2Te) 78.5 film, with a fast crystallization speed of 52 ns and a low amorphization power of 35 mW. This journal is

(ZnO)x(Sb2Te3)1-x materials with different ZnO contents have been systemically studied with an aim of finding the most suitable composition for phase change memory applications. It was found that ZnO-doping could improve thermal stability and electrical behavior of Sb2Te3 film. Sb2Te3-rich nanocrystals, surrounded by ZnO-rich amorphous phases, were observed in annealed ZnO-doped Sb2Te3 composite films, and the segregated domains exhibited a relatively uniform distribution. The ZnO-doped Sb2Te3 composite films, especially with 5.2 at% ZnO concentration were found to have higher crystallization temperature, higher crystalline resistance, and faster crystallization speed in comparison with Ge2Sb2Te5. A reversible repetitive optical switching behavior can be observed in (ZnO)5.2(Sb2Te 3)94.8, confirming that the ZnO doping is responsible for a fast switching and the compound is stable with cycling. Therefore, it is promising for the applications in phase change memory devices.

ZnxSb100-x films with low Zn content are crystallized in a single-step process with Sb, while the film (Zn/Sb ratio is about 1:1) exhibits a two-step crystallization process with ZnSb metastable and stable phases. Importantly, ZnSb films have higher crystallization temperature (~257 °C), larger crystalline activation energy (~5.63 eV), better 10 year-data-retention (~201 °C) and lower melting temperature (~500 °C).

Zn-doped Sb₂Te films are proposed to present the feasibility for phase-change memory application. Zn atoms are found to significantly increase crystallization temperature of Zn x (Sb₂Te)1−x films and be almost linearly with the wide range of Zn-doping concentration from x = 0 to 29.67 at.%. Crystalline resistances are enhanced by Zn-doping, while keeping the large amorphous/crystalline resistance ratio almost constant at ∼10⁵. Especially, the Zn 26.07 (Sb₂Te)73.93 and Zn 29.67 (Sb₂Te)70.33 films exhibit a larger resistance change, faster crystallization speed, and better thermal stability due to the formation of amorphous Zn-Sb and Zn-Te phases as well as uniform distribution of Sb₂Te crystalline grains.

The superior performance of Zn-doped Sb₇Te₃ films might be favorable for the application in phase change memory. It was found that Zn dopants were able to suppress phase separation and form single stable Sb2Te crystal grain, diminish the grain size, and enhance the amorphous thermal stability of Sb₇Te₃ film. Especially, Zn 30.19(Sb₇Te₃)69.81 film has higher crystallization temperature (∼258 °C), larger crystallization activation energy (∼4.15 eV), better data retention (∼170.6 °C for 10 yr), wider band gap (∼0.73 eV), and higher crystalline resistance. The minimum times for crystallization of Zn 30.19(Sb₇Te₃)69.81 were revealed to be as short as ∼10 ns at a given proper laser power of 70 mW.

In this paper, we deposited amorphous chalcogenide Ge-Sb-Se films using the RF sputtering method, then measured their optical and structural properties using various diagnosis tools. The linear refractive index and optical band-gap for as-deposited films

Mg-doped Ge2Sb2Te5 (GST) films with different Mg doping concentrations have been prepared, and their crystallization behavior, structure and electrical properties have been systematically investigated for phase-change memory applications. The results show that the addition of Mg into GST films could result in an enhancement in crystallization temperature, activation energy and electrical resistance compared with the conventional GST films, indicating that a good amorphous thermal stability. On the other hand, the proper Mg concentration ranging from 13.6 to 31.1 at.% can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase and suppress the formation of the hexagonal close-packed (hcp) crystalline phase. X-ray photoelectron spectra (XPS) further confirm that the formation of covalent MgSb and MgTe bonds contribute to the enhanced thermal stability in Mg-doped GST films.

We deposited Ge28Sb12Se60 chalcogenide films using either thermal evaporation or radio-frequency magnetron sputtering techniques, and then measured their structural and optical properties using various diagnosis tools. The refractive indices of the films

This study reports on the synthesis of tellurium-based chalcogenide films that have high thermal stability for phase change memory application. Several Te-based chalcogenide alloys of In-Bi-Te, Ag-Bi-Te, In-Sb-Te, Sn-Sb-Te, Zn-Ge-Te, and Ga-Ge-Te are reported. Their thermal, optical, and electrical properties are investigated. The results show that Bi-Te-based films have a higher crystallization temperature and greater activation energy compared with the other Sb-Te-based and Ge-Te-based films. Especially, In₂.₈Bi₃₆.₆Te₆₀.₆film exhibits high crystallization temperature (252 °C) and great activation energy (5.16 eV), showing much improved amorphous thermal stability. A relatively wider optical band gap (0.674 eV) of thermal annealed In₂.₈Bi₃₆.₆Te₆₀.₆film is obtained. In addition, it also has a higher amorphous/crystalline resistance ratio of about 10⁵, implying that current consumption could be low in the phase-change memory operation.

Ge 2Sb 2Te 5 films were locally crystallized by a tightly focused laser beam and the structural evolution was studied by Raman scatting. The marks recorded by a broad range of laser power were studied by optical microscope. Raman spectra of films with irradiation power of 0.1 mW and 1 mW were consistent with those of films annealed at 140°C and 400°C, respectively. It reveals that both the cubic and hexagonal crystalline phases have been achieved under the irradiation of 488 nm laser in amorphous Ge 2Sb 2Te 5 films. Specifically, the appearance of a new band of ∼141 cm -1 in films with irradiation power larger than 1.25 mW confirms that the over-irradiation causes the segregation of Te crystalline phase in films.

The thermal and electrical properties of Zn 1.25Sb 2Te 3 film have been investigated for phase change memory (PCM) applications. Compared with the conventional Ge 2Sb 2Te 5, Zn 1.25Sb 2Te 3 film exhibits a higher crystallization temperature (∼200°C), g