SbOx Thin Films Used for Write-Once Blue Laser Recording

SbOx thin films are deposited by reactive dc-magnetron sputtering from an antimony metal target in Ar＋O2 with the relative O2 content 7%. It is found that the as-deposited films can represent a two-component system comprising amorphous Sb and amorphous Sb2 O3. The crystallization of Sb is responsible for the changes of optical properties of the films. The results of the static test show that the SbOx thin films have good writing sensitivity for blue laser beams and the recording marks are very clear and circular. High reflectivity contrast of about 41% is obtained at a writing power 6mW and writing pulse width 300ns. In addition, the films show a good stability after reading 10000 times.     

Characteristics of Sn-Doped Ge2Sb2Te5 Films Used for Phase-Change Memory

Sn-doped Ge2Sb2Te5 thin films deposited on Si（100）/SiO2 substrates by rf magnetron sputtering are investigated by a differential scanning calorimeter, x-ray diffraction and sheet resistance measurement. The crystallization temperatures of the 3.58 at.%, 6.92 at.% and 10.04 at.% Sn-doped Ge2Sb2Te5 thin films have decreases of 5.3, 6.1 and 0.9℃, respectively, which is beneficial to reduce the switching current for the amorphous-to-crystalline phase transition. Due to Sn-doping, the sheet resistance of crystalline Ge2Sb2Te5 thin films increases about 2-10 times, which may be useful to reduce the switching current for the amorphous-to-crystalline phase change. In addition, an obvious decreasing dispersibility for the sheet resistance of Sn-doped Ge2Sb2Te5 thin films in the crystalline state has been observed, which can play an important role in minimizing resistance difference for the phase-change memory cell element arrays.     

Thermal phase change and activation energy of crystallization of Ge-Sb-Te-Sn thin films

To improve the optical storage performance, Sn was doped into Ge2Sb2Te5 phase change thin films. The optical and thermal properties of Sn-doped Ge2Sb2Te5 film were investigated. The crystal structures of the as-sputtered and the annealed films were identified by the X-ray diffraction (XRD) method. The differential scanning calorimeter (DSC) method is used to get the crystallization temperature and crystallization energy (Ea). It was found that proper Sn-doping could highly improve storage performance of the Ge2Sb2Te5 media.     

EXAFS STUDY OF THE LOCAL STRUCTURE NANOCRYSTALLINE FeZrB(Cu) SOFT MAGNETIC ALLOYS

The changes of local structures around Fe and Zr atoms in the nanocrystalline films of Fe₈₅Zr₉B₆ and Fe₈₄Zr₉B₆ Cu₁ alloys during annealing process were investigated by extended X-ray absorption fine structure (EXAFS) technique. It is confirmed that Zr atoms always exist in amorphous phase and do not dissolve in the bcc α-Fe crystalline phase. The addition of 1 at% Cu lowers the crystallization temperature.     

STUDIES OF NANOCRYSTALLINE PHASE AND RESIDUAL AMORPHOUS PHASE OF FeCuNbSiB ALLOY

The σ-T and dσ/dT-T curves of the FeCuNbSiB amorphous alloy, which are the relationship between "apparent weight loss" and tempera ture, are investigated by magnetic thermogravimetry analysis (MTGA) technique. It is found that the crystallization process of the samples can be divided into five stages. The studies of samples annealed in the temperature range of 480-610℃ for 1 h show that when the annealing temperature (T_a) is lower than 540℃, the quantity of nanocrystalline α-Fe(Si) phase increases evidently with T_a, and the Curie temperature (T_c) of residual amorphous phase also increases linearly with T_a, i.e., T_c=0.52T_a+91.7℃, with correlation coefficient γ=0.98. The variation of volume fraction of α-Fe(Si) nanocrystalline phase or residual amorphous phase with T_a is measured.     

Optical properties of glasses activated by the compounds CuInSe2 and CuInTe2 and by the solid solutions CuInSe2x Te(1−x)

The spectral properties of amorphous media synthesized on the basis of glasses of the system SiO₂-CaO-R₂O (R=Na, K, Li), the ternary compounds CuInSe₂, and CuInTe₂, and solid solutions based on them have been investigated. It is shown that the absorption limit of the media investigated lies within 1.4–1.6 μm. It is noted that the three alkali ions constituting the system exert a favorable influence on the state and optical properties of the amorphous media activated with the compound CuInTe₂ and with the solid solutions CuInSe_2xTe_(1−x), where x≤0.5. The influence of the concentration of the solid solution CuInSeTe (x=0.5) on the optical properties of the amorphous media is investigated. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 132–134, January–February, 2000.     

Characteristics of Sb_6Te_4/VO_2 Multilayer Thin Films for Good Stability and Ultrafast Speed Applied in Phase Change Memory

The Sb_6Te_4/VO_2 multilayer thin films are prepared by magnetron sputtering and the potential application in phase change memory is investigated in detail. Compared with Sb_6Te_4, Sb_6Te_4/VO_2 multilayer composite thin films have higher phase change temperature and crystallization resistance, indicating better thermal stability and less power consumption. Also, Sb_6Te_4/VO_2 has a broader energy band of 1.58 eV and better data retention(125℃ for 10 y). The crystallization is suppressed by the multilayer interfaces in Sb_6Te_4/VO_2 thin film with a smaller rms surface roughness for Sb_6Te_4/VO_2 than monolayer Sb_4Te_6. The picosecond laser technology is applied to study the phase change speed. A short crystallization time of 5.21 ns is realized for the Sb_6Te_4(2 nm)/VO_2(8 nm)thin film. The Sb_6Te_4/VO_2 multilayer thin film is a potential and competitive phase change material for its good thermal stability and fast phase change speed.     

STUDIES ON INFRARED AND PHOTOLUMINESCENCE PROPERTIES OF CdIn2O4 FILMS DEPOSITED BY RF REACTIVE SPUTTERING

Transparent and conductive CdIn₂O₄(CIO) thin films were prepared successfully by rf reactive sputtering from a Cd-In alloy target in an Ar+O₂ atmosphere. The measurement of transmission and reflection spectra, at wavelengths between 0.2 and 6.0μm, and photoluminescence spectrum of the films are reported. The optical properties of the films are analyzed and discussed in detail. Two reasonable methods for calculating the effective mass of the free carrier in the films are presented.     

Optical characterization of antimony-based bismuth-doped thin films with different annealing temperatures

Antimony-based bismuth-doped thin film,a new kind of super-resolution mask layer,is prepared by magnetron sputtering.The structures and optical constants of the thin films before and after annealing are examined in detail.The as-deposited film is mainly in an amorphous state.After annealing at 170-370℃,it is converted to the rhombohedral-type of structure.The extent of crystallization increased with the annealing temperature.When the thin film is annealed,its refractive index decreased in the most visible region,whereas the extinction coefficient and reflectivity are markedly increased.The results indicate that the optical parameters of the film strongly depend on its microstructure and the bonding of the atoms.     

Electrical properties of the high-pressure phases of gallium and indium tellurides

A study has been made of the resistance ρ, the thermopower S, and magnetoresistance MR of Ga₂Te₃ and α-In₂Te₃ single crystals at pressures P up to 25 GPa. It is found that the resistance ρ and |S| sharply decrease at ∼0–5 and 1.5–3 GPa, respectively. The semiconductor-metal phase transitions in the temperature range from 77 to 300 K are established from the sign reversal of the temperature coefficient of ρ to occur at P>4.4 and >1.9 GPa. The values S ≈+(10–20)μ V/K for the metallic phases with a Bi₂Te₃-type structure agree with those for liquid In₂Te₃ and Ga₂Te₃. Negative MR is revealed in In₂Te₃ at P≈1.9 GPa. No MR is observed in Ga₂Te₃ up to 25 GPa. The variation of the electronic structure of In₂Te₃ and Ga₂Te₃ under pressure is discussed. __________ Translated from Fizika Tverdogo Tela, Vol. 42, No. 6, 2000, pp. 1004–1008. Original Russian Text Copyright ? 2000 by Shchennikov, Savchenko, Popova.     

In situ AFM and Raman spectroscopy study of the crystallization behavior of Ge2Sb2Te5 films at different temperature

Using in situ atomic force microscope (AFM) and Raman spectroscopy, the real-time crystallization properties of Ge₂Sb₂Te₅ films at different temperature were characterized. The given AFM topograph and phase images revealed that the structure of amorphous Ge₂Sb₂Te₅ films began to change at a temperature of as low as 100 °C. When the temperature reached 130 °C, some crystal fragments had formed at the film surface. Heating up to 160 °C, the size of the visible crystal fragments increased, but decreased at a higher temperature of 200 °C. When the Ge₂Sb₂Te₅ film was cooled down to room temperature (RT) from 200 °C, the crystal fragments divided into crystal grains due to the absence of heating energy. The Raman spectra at different temperature further verified the structure evolution of the Ge₂Sb₂Te₅ film with temperature. This work is of significance for the preparation of Ge₂Sb₂Te₅ films and the erasing of data.     

氮掺杂Ge2Sb2Te5相变存储器的多态存储功能

通过反应溅射的方法，制备了N掺杂的Ge₂Sb₂Te₅(N-GST)薄膜，用作相变存储器的存储介质.研究表明，掺杂的N以GeN的形式存在，不仅束缚了Ge₂Sb₂Te₅ (GST)晶粒的长大也提高了GST的晶化温度和相变温度.利用N-GST薄膜的非晶态、晶态面心立方相和晶态六方相的电阻率差异，能够在同一存储单元中存储三个状态，实现相变存储器的多态存储功能. 关键词： 相变存储器 多态存储 N掺杂 2Sb₂Te₅')" href="#">Ge₂Sb₂Te₅     

基于Si掺杂Sb2Te3薄膜的相变存储器研究

采用磁控三靶(Si，Sb及Te)共溅射法制备了Si掺杂Sb₂Te₃薄膜，作为对比，制备了Ge₂Sb₂Te₅和Sb₂Te₃薄膜，并且采用微加工工艺制备了单元尺寸为10μm×10μm的存储器件原型来研究器件性能.研究表明，Si掺杂提高了Sb₂Te₃薄膜的晶化温度以及薄膜的晶态和非晶态电阻率，使得其非晶态与晶态电阻率之比达到10⁶，提高了器件的电阻开/关比；同Ge₂Sb₂Te₅薄膜相比，16at% Si掺杂Sb₂Te₃薄膜具有较低的熔点和更高的晶态电阻率，这有利于降低器件的RESET电流.研究还表明，采用16at% Si掺杂Sb₂Te₃薄膜作为存储介质的存储器器件原型具有记忆开关特性，可以在脉高3V、脉宽500ns的电脉冲下实现SET操作，在脉高4V、脉宽20ns的电脉冲下实现RESET操作，并能实现反复写/擦，而采用Ge₂Sb₂Te₅薄膜的相同结构的器件不能实现RESET操作. 关键词： 相变存储器 硫系化合物 2Te₃薄膜')" href="#">Si掺杂Sb₂Te₃薄膜 SET/RESET转变     

相变存储材料Ge1Sb2Te4和Ge2Sb2Te5薄膜的结构和电学特性研究

采用射频磁控溅射方法制备了两种用于相变存储器的Ge₁Sb₂Te₄和Ge₂Sb₂Te₅相变薄膜材料,对其结构、电学输运性质和恒温下电阻随时间的变化关系进行了比较和分析.X射线衍射(XRD)和原子力显微镜(AFM)的结果表明:随着退火温度的升高,Ge₁Sb₂Te₄薄膜逐步晶化,由非晶态转变为多晶态,表面出现均匀的、 关键词： 硫系相变材料 1Sb₂Te₄')" href="#">Ge₁Sb₂Te₄ 2Sb₂Te₅')" href="#">Ge₂Sb₂Te₅     

Effects of carbon doping on chemical states of amorphous Ge2Sb2Te5, measured with synchrotron radiation

We fabricated and analyzed the chemical states of carbon-doped (5.2–13.2 at.%) Ge₂Sb₂Te₅ thin films on Si substrates using high-resolution, X-ray photoelectron spectroscopy with synchrotron radiation. Thin films were completely amorphous and their phase-change temperature was 150 °C higher than for un-doped GST. As the carbon doping concentration increased, new chemical states of Ge 3d with 29.9 eV and C 1s with 283.7 eV core-levels were observed. The doped carbon was bonded only with Ge in GST and doping was saturated at 8.7 at.%.     

Performance improvement of Sb2Te3 phase change material by Al doping

Al doped Sb₂Te₃ material was proposed to improve the performance of phase-change memory. Crystallization temperature, activation energy, and electrical resistance of the Al doped Sb₂Te₃ films increase markedly with the increasing of Al concentration. The additional Al-Sb and Al-Te bonds enhance the amorphous thermal stability of the material. Al_0.69Sb₂Te₃ material has a better data retention (10 years at 110 °C) than that of Ge₂Sb₂Te₅ material (10 years at 87 °C). With a 100 ns width voltage pulse, SET and RESET voltages of 1.3 and 3.3 V are achieved for the Al_0.69Sb₂Te₃ based device.     

Effects of nitrogen doping on the properties of Ge15Sb85 phase-change thin film

The effects of nitrogen doping on the chemical bonding state, microstructure, electrical property and thermal stability of Ge₁₅Sb₈₅ film were investigated in detail. The doped N atoms tend to bond with Ge to form Ge₃N₄, as proved by X-ray photoelectron spectroscopy analyses. X-ray diffraction patterns showed that both undoped and N-doped Ge₁₅Sb₈₅ films crystallize into a hexagonal phase very similar to Sb. The thickness reduction upon crystallization for undoped and N-doped Ge₁₅Sb₈₅ films is less than 5%. The crystalline resistivity, crystallization temperature, and thermal stability of amorphous state all increase after nitrogen doping, while the grain size decreases. By adding 7.0 at.% N into the Ge₁₅Sb₈₅ film, the crystalline resistivity increases twelve times and the crystallization temperature increases about 50 °C. The maximum temperature for 10-year retention of amorphous Ge₁₅Sb₈₅ film is estimated to be 147 °C and that of N-doped films is even higher, which will promise better data retention of phase-change random access memory especially in the high-temperature application.     

Characteristics of Si-doped Sb2Te3 thin films for phase-change random access memory

The characteristics of Si-doped Sb₂Te₃ thin films were investigated using differential scanning calorimetry (DSC), four-point probe technique, X-ray diffraction (XRD) analysis and high resolution transmission electron microscopy (HRTEM). It is found that the as-deposited Sb₂Te₃ film in our study is partly crystallized. Silicon doping increases the crystallization temperature and resistivity of Sb₂Te₃ film significantly. XRD and HRTEM analyses indicated that some of the doped Si atoms substitute for Sb or Te in the lattice, while others exists at the grain boundaries in the form of amorphous phase, which may be responsible for grain size reduction and high crystalline resistivity of Si-doped specimens. Compared with the conventional Ge₂Sb₂Te₅ film, Si-doped Sb₂Te₃ films exhibit lower melting temperature and higher crystalline resistivity, which is beneficial to RESET current reduction of phase-change random access memory (PRAM). These results show the feasibility of Si-doped Sb₂Te₃ films in PRAM application.     

Effective method for preparation of oxide-free Ge2Sb2Te5 surface: An X-ray photoelectron spectroscopy study

Cleaning the surfaces of the as-deposited Ge₂Sb₂Te₅ was studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD). The mixed native oxides on the as-deposited Ge₂Sb₂Te₅ surface can be easily removed by dipping Ge₂Sb₂Te₅ in de-ionized water for 1 min, while the surface morphology remains unchanged after cleaning. Native oxides only re-grow after exposure to air for more than 4 min. Although dipping in water leads to a surface layer deficient in Ge and Sb, the surface composition of Ge₂Sb₂Te₅ can recover to its stoichiometric value after annealing at 200 °C in vacuum. The phase remains amorphous at room temperature after dipping in water, and changes to fcc and hcp after annealing at 100 and 220 °C, respectively.     

Ge/Sb2Te3 nanocomposite multilayer films for high data retention phase-change random access memory application

The amorphous-to-crystalline transition of Ge/Sb₂Te₃ nanocomposite multilayer films with various thickness ratios of Ge to Sb₂Te₃ were investigated by utilizing in situ temperature-dependent film resistance measurements. The crystallization temperature and activation energy for the crystallization of the multilayer films increased with the increase in thickness ratio of Ge to Sb₂Te₃. The difference in sheet resistance between amorphous and crystalline states could reach as high as 10⁴ Ω/□. The crystallization temperature and activation energy for the crystallization of Ge/Sb₂Te₃ nanocomposite multilayer films was proved to be larger than that of conventional Ge₂Sb₂Te₅ film, which ensures a better data retention for phase-change random access memory (PCRAM) use. A data retention temperature for 10 years of the amorphous state [Ge (2 nm)/Sb₂Te₃ (3 nm)]₄₀ film was estimated to be 165 °C. Transmission electron microscopy (TEM) images revealed that Ge/Sb₂Te₃ nanocomposite multilayer films had layered structures with clear interfaces.