The feasibility of Sn, In, or Al doped ZnSb thin film as candidates for phase change material

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.This work was financially supported by the Natural Science Foundation of China (Grant Nos. 61306147, 61377061), the Public Project of Zhejiang Province (Grant No.2014C31146), the Young Leaders of academic climbing project of the Education Department of Zhejiang Province (pd2013092), the Natural Science Foundation of Zhejiang Province (Grant No. LQ15F040002), the Scientific Research Foundation of Graduate School of Ningbo University, and sponsored by K. C. Wong Magna Fund in Ningbo University

Enhanced thermal stability and electrical behavior of Zn-doped Sb2Te films for phase change memory application

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

Phase change behaviors of Zn-doped Ge2Sb2Te5 films

This work was financially supported by the Program for New Century Excellent Talents in University (Grant No. NCET-10-0976), the International Science & Technology Cooperation Program of China (Grant No. 2011DFA12040), the National Program on Key Basic Research Project (973 Program) (Grant No. 2012CB722703), the Natural Science Foundation of China (Grant Nos. 61008041 and 60978058), the Natural Science Foundation of Zhejiang Province, China (Grant No. Y1090996), the Natural Science Foundation of Ningbo City, China (Grant No. 2011A610092), the Program for Innovative Research Team of Ningbo city (Grant No. 2009B21007), and sponsored by K. C. Wong Magna Fund in Ningbo University

Magnetic field induced discontinuous spin reorientation in ErFeO3 single crystal

The spin reorientation of ErFeO3 that spontaneously occurs at low temperature has been previously determined to be a process involving the continuous rotation of Fe3þ spins. In this work, the dynamic process of spin reorientation in ErFeO3 single crystal has been investigated by AC susceptibility measurements at various frequencies and static magnetic fields. Interestingly, two completely discontinuous steps are induced by a relatively large static magnetic field due to the variation in the magnetic anisotropy during this process. It provides deeper insights into the intriguing magnetic exchange interactions which dominate the sophisticated magnetic phase transitions in the orthoferrite systems

Glass formation and properties of Ge-Ga-Te-ZnI2 far infrared chalcohalide glasses

International audienceIn order to develop novel far infrared window material, a series of Ge-Ga-Te-ZnI2 chalcohalide glasses were prepared by traditional melt-quenching method and their glass-forming region was determined also. Here, some measurements including X-ray diffraction (XRD), differential thermal analysis (DTA), UV-Vis-NIR absorption spectrum, and infrared optical transmission spectra were carried out. The allowed indirect transition optical band gap was calculated according to the classical Tauc equation. The results show that with the addition of ZnI2, the glass-forming ability and thermal stability are improved gradually. With the contents of ZnI2 increased from 5 to 20 at.%, continued blue-shifting occurs in the cutting-off absorption edge of short-wavelength and the values of indirect optical band gaps were observed with ranges from 0.596 to 0.626 eV in these glasses. These GeTe4.3-GaTe3-ZnI2 glasses show wide optical transmission and the infrared cut-off wavelengths are larger than 25 μm, which implies that the Ge-Ga-Te-ZnI2 chalcogenide glasses possess the potential of far-IR optical window applications

Te-based chalcogenide films with high thermal stability for phase change memory

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.This work was financially supported by the Natural Science Foundation of China (Grant Nos. 61008041, 61107047, and 60978058), the Natural Science Foundation of Zhejiang Province, China (Grant No. Y1090996), the Natural Science Foundation of Ningbo City, China (Grant No. 2011A610092), the Ningbo optoelectronic materials and devices creative team (Grant No. 2009B21007), the Open Research Fund of State Key Laboratory of Transient Optics and Photonics, Chinese Academy of Sciences (Grant No. SKLST201010), and sponsored by K. C. Wong Magna Fund in Ningbo University

Freely adjusted properties in Ge–S based chalcogenide glasses with iodine incorporation

International audienceIn this study, we examined the function of halogen iodine acting as a glass network modifier in green chalcogenide glasses based on the Ge–S system. We obtained a series of Ge–S–I glasses and determined their glass-forming region. We then recorded the physical, thermal, and optical properties and studied the effect of halogen iodine on Ge–S–I glasses. Results show that these glasses have relatively wide optical transmission window for infrared (IR) applications. The softening temperature of Ge–S–I glasses varies from 210.54 °C to 321.63 °C, this temperature fits well with some kinds of high-temperature polymers, such as PES and PEI, the polymers serve as protective layers with high strength and flexibility, thus simplifying the fabrication processes of IR chalcogenide glass fiber. Finally, we performed a purification process to eliminate impurities and to improve optical spectr