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1.
Phase-change nonvolatile memory cell elements composed of Sb2Te3 chalcogenide have been fabricated by using the focused ion beam method. The contact size between the Sb2Te3 phase change film and electrode film in the cell element is 2826 nm2 (diameter: 60 nm). The thickness of the Sb2Te3 chalcogenide film is 40 nm. The threshold switching current of about 0.1 mA was obtained. A RESET pulse width as short as 5 ns and the SET pulse width as short as 22 ns for Sb2Te3 chalcogenide can be obtained. At least 1000 cycle times with a RESET/SET resistance ratio >30 times is achieved for Sb2Te3 chalcogenide C-RAM cell element. 相似文献
2.
Hangbing Lv Yinyin Lin Tingao Tang Yunfeng Lai Bingchu Cai 《Microelectronics Journal》2006,37(9):982-984
Impacts of annealing temperature and film thickness to the resistivity of Ge2Sb2Te5(GST) have been studied. The resistivity of GST drops when the annealing temperature reaches 180 °C, rises above 360 °C and the thicker film crystallized more easily. Electronic device of phase change memory also has been fabricated with metal sidewall technology using 5 μm lithographic technology. The device was successfully programmed by 100 ns of 5 V pulse for SET and 10 ns of 10 V pulse for RESET. More than 100 times on/off ratio has been reached. 相似文献
3.
Sang-Ouk Ryu 《Journal of Electronic Materials》2008,37(4):535-539
A phase-change memory device that utilizes an antimony (Sb)-excess Ge15Sb47Te38 chalcogenide thin film was fabricated and its electrical properties were measured and compared with a similar device that
uses Ge22Sb22Te56. The resulting electrical characteristics exhibited I
reset values of 14 mA for Ge22Sb22Te56 and 10.6 mA for Ge15Sb47Te38. Also, the set operation time (t
set) for the device using Ge15Sb47Te38 films was 140 ns, which was more than twice as fast as the Ge22Sb22Te56 device. The relationship between the microstructure and the improved electrical performance of the device was examined by
means of transmission electron microscopy (TEM). 相似文献
4.
本文制备了纳米级Hf/HfO2阻变存储器(RRAM)。RRAM顶层电极和底部电极交叉,从而形成了金属-氧化物-金属结构。系统地研究了RRAM的电学特性,包括forming过程,SET过程和RESET过程。讨论了SET电压和RESET电压的相关性,以及高阻态和低阻态的相关性。RRAM的电学特性与SET过程中的限制电路强相关。可以基于量子点接触模型,阐述纳米级Hf/HfO2阻变存储器的导通机制。 相似文献
5.
Crystallization properties of Sb-rich GeSbTe alloys by in-situ morphological and electrical analysis
Phase Change Memory (PCM) operation relies on the reversible transition between two stable states (amorphous and crystalline) of a chalcogenide material, mainly of composition Ge2Sb2Te5 (GST). In Wall type PCM cells, cycling endurance induces a gradual change of the cell electrical parameters caused by variations in the chemical composition of the active volume. The region closer to the GST-heater contact area, becomes more Sb rich and Ge depleted. The new alloy has usually different thermal characteristics for the phase transitions that influence the electrical behavior of the cell. In this study we analyze the morphological, structural and electrical properties of two Sb-rich non-stoichiometric alloys: Ge14Sb35Te51 and Ge14Sb49Te37, at their amorphous and crystalline phase. Experiments have been performed in non-patterned blanket films and, to simulate the device size, in amorphous regions of 20 nm, 50 nm and 100 nm diameter respectively. The amorphous Ge14Sb35Te51 film crystallizes in the meta-stable face centered cubic structure at 150 °C and in the rhombohedral phase at 175 °C, behavior characteristic of the Ge1Sb2Te4 composition. The average grain size is of about 100 nm after an annealing at 400 °C. The Ge14Sb49Te37 film crystallizes only in the hexagonal phase, with an average grain size of about 60 nm after annealing at 400 °C. The X-ray fluorescence analysis shows a non uniform distribution of the constituent atoms and in particular a Ge signal decrement and a Sb enrichment at grain boundaries. The in situ annealing of amorphous nano-areas (RESET state under a thermal stress) indicates a fast re-crystallization speed for Ge14Sb35Te51, 80 pm/s at 90 °C, and a lower speed for Ge14Sb49Te37, at 130 °C a grain growth velocity of 50 pm/s has been measured. The different behavior of the two alloys is discussed in terms of structural vacancies filling by the Sb atoms in excess and by their segregation at grain boundaries. The influence of the obtained results on the device characteristics is discussed. 相似文献
6.
X-ray diffraction patterns and resistivity measurement indicate that as-deposited N-doped Sb2Te3 (STN) films become amorphous while the as-deposited Sb2Te3 film is crystalline. A lateral as-deposited STN-based multi-layer phase change memory was proposed for multi-state storage. The active region of the device consists of a top 30-nm TiN/180-nm STN/20-nm TiN/bottom 120-nm STN stacked multi-layer. Static switching properties of the device with STN initially starting from the amorphous state exhibit two apparent S-shaped switchings, which correspond to two marked device resistance drops by a factor of 2-5. The first and second threshold voltages are around 2.8-3.2 and 4.3-5.4 V, respectively. Finite element analysis of the device shows that the two switchings could sequentially occur at the electrode steps from the bottom 120-nm STN layer to the top thick 180-nm STN layer. 相似文献
7.
Resistive switching behavior of HfO2 high-k dielectric has been studied as a promising candidate for emerging non-volatile memory technology. The low resistance ON state and high resistance OFF state can be reversibly altered under a low SET/RESET voltage of ±3 V. The memory device shows stable retention behavior with the resistance ratio between both states maintained greater than 103. The bipolar nature of the voltage-induced hysteretic switching properties suggests changes in film conductivity related to the formation and removal of electronically conducting paths due to the presence of oxygen vacancies induced by the applied electric field. The effect of annealing on the switching behavior was related to changes in compositional and structural properties of the film. A transition from bipolar to unipolar switching behavior was observed upon O2 annealing which could be related to different natures of defect introduced in the film which changes the film switching parameters. The HfO2 resistive switching device offers a promising potential for high density and low power memory application with the ease of processing integration. 相似文献
8.
X.M. Long X.S. Miao J.J. Sun X.M. Cheng H. Tong Y. Li D.H. Yang J.D. Huang C. Liu 《Solid-state electronics》2012,67(1):1-5
In this paper, the volume-minimized model of phase change memory (PCM) cell with Ge2Sb2Te5 (GST) material has been established to study the dynamic switching (set-to-reset) characteristic dependence on the sidewall angle. Joule heating volume, threshold current, dynamic resistance and phase transition rate of PCM cells by current pulse are all calculated. The results show that the threshold current increases with decreasing the sidewall angle and is significantly impacted by the feature size and aspect ratio. The PCM cell of 90° sidewall angle exhibits the smallest Joule heating volume, the highest RESET resistance and the fastest phase transition property. 相似文献
9.
A thermoelectric thin-film device of the cross-plane configuration was fabricated by flip-chip bonding of the top electrodes to 242 pairs of electrodeposited n-type Bi2Te3 and p-type Sb2Te3 thin-film legs on the bottom substrate. The electrodeposited Bi2Te3 and Sb2Te3 films of 20-μm thickness exhibited Seebeck coefficients of ?59 μV/K and 485 μV/K, respectively. The internal resistance of the thin-film device was measured as 3.7 kΩ, most of which was attributed to the interfacial resistance of the flip-chip joints. The actual temperature difference ΔT G working across the thin-film legs was estimated to be 10.4 times smaller than the apparent temperature difference ΔT applied across the thin-film device. The thin-film device exhibited an open-circuit voltage of 0.294 V and a maximum output power of 5.9 μW at an apparent temperature difference ΔT of 22.3 K applied across the thin-film device. 相似文献
10.
Chia-Jyi Liu Gao-Jhih Liu Chun-Wei Tsao Yo-Jhih Huang 《Journal of Electronic Materials》2009,38(7):1499-1503
We report on the successful hydrothermal synthesis of Bi0.5Sb1.5Te3, using water as the solvent. The products of the hydrothermally prepared Bi0.5 Sb1.5Te3 were hexagonal platelets with edges of 200–1500 nm and thicknesses of 30–50 nm. Both the Seebeck coefficient and electrical
conductivity of the hydrothermally prepared Bi0.5Sb1.5Te3 were larger than those of the solvothermally prepared counterpart. Hall measurements of Bi0.5Sb1.5Te3 at room temperature indicated that the charge carrier was p-type, with a carrier concentration of 9.47 × 1018 cm−3 and 1.42 × 1019 cm−3 for the hydrothermally prepared Bi0.5Sb1.5Te3 and solvothermally prepared sample, respectively. The thermoelectric power factor at 290 K was 10.4 μW/cm K2 and 2.9 μW/cm K2 for the hydrothermally prepared Bi0.5Sb1.5Te3 and solvothermally prepared sample, respectively. 相似文献
11.
Vijayaharan A. Venugopal Giampiero Ottaviani Camillo Bresolin Davide Erbetta Alberto Modelli Enrico Varesi 《Journal of Electronic Materials》2009,38(10):2063-2068
The thermal stability of a Ge2Sb2Te5 chalcogenide layer in contact with titanium and titanium nitride metallic thin films has been investigated mainly using x-ray
diffraction and elastic nuclear backscattering techniques. Without breaking vacuum, Ti and TiN have been deposited on Ge2Sb2Te5 material using magnetron sputtering. Thermal treatments have been performed in a 10−7 mbar vacuum furnace. On annealing up to 450°C, the TiN metallic film does not interact with the chalcogenide film, but at
the same time adhesion problems and instabilities in contact resistance arise. To improve the adhesion and eventually stabilize
the contact resistance, an interfacial Ti layer has been considered. At 300°C, a TiTe2 compound is formed by interacting with Te segregated from the Ge2Sb2Te5 layer. At higher temperatures, the Ti layer decomposes the chalcogenide film, forming several compounds tentatively identified
as GeTe, Ge3Ti5, Ge5Ti6, TiTe2,, and Sb2Te3. It has been found that the properties of the Ge2Sb2Te5 film can be retained by controlling the decomposition rate of the chalcogenide layer, which is achieved by providing a limited
supply of Ti and/or by depositing a Te-rich Ge2Sb2Te5 film. 相似文献
12.
Ming Tan Yuan Deng Yao Wang Bingwei Luo Lixing Liang Lili Cao 《Journal of Electronic Materials》2012,41(11):3031-3038
An approach for fabrication of highly (0?0?l)-textured Sb2Te3 thin film with layered structure by the magnetron sputtering method is reported. The composition, microstructure, and thermoelectric properties of the thin films have been characterized and measured by x-ray diffraction, scanning electron microscopy with energy-dispersive x-ray spectroscopy, and a thermoelectric (TE) measurement system, respectively. The results show that well-oriented (0?0?l) Sb2Te3 thin film with layered structure is beneficial for improvement of thermoelectric properties, being a promising choice for planar TE devices. The power generation and cooling performance of a layered p-Sb2Te3 film device are superior to those of the ordinary thin-film device. For a typical parallel device with 38 layered Sb2Te3 film elements, the output voltage, maximum power, and corresponding power density are up to 10.3?mV, 11.1?μW, and 73?mW/cm2, respectively, for a temperature difference of 76?K. The device can produce a 6.1?K maximum temperature difference at current of 45?mA. The results prove that enhanced microdevice performance can be realized by integrating (0?0?l)-oriented Sb2Te3 thin films with a layered architecture. 相似文献
13.
Sung-Do Kwon Byeong-kwon Ju Seok-Jin Yoon Jin-Sang Kim 《Journal of Electronic Materials》2009,38(7):920-924
Bismuth–antimony–telluride based thin film materials were grown by metal organic vapor phase deposition (MOCVD). A planar-type
thermoelectric device was fabricated with p-type Bi0.4Sb1.6Te3 and n-type Bi2Te3 thin films. The generator consisted of 20 pairs of p-type and n-type legs. We demonstrated complex structures of different conduction types of thermoelectric elements on the same substrate
using two separate deposition runs of p-type and n-type thermoelectric materials. To demonstrate power generation, we heated one side of the sample with a heating block and
measured the voltage output. An estimated power of 1.3 μW was obtained for the temperature difference of 45 K. We provide a promising procedure for fabricating thin film thermoelectric
generators by using MOCVD grown thermoelectric materials that may have a nanostructure with high thermoelectric properties. 相似文献
14.
The electrochemical behavior of nonaqueous dimethyl sulfoxide solutions of BiIII, TeIV, and SbIII was investigated using cyclic voltammetry. On this basis, Bi
x
Sb2−x
Te
y
thermoelectric films were prepared by the potentiodynamic electrodeposition technique in nonaqueous dimethyl sulfoxide solution,
and the composition, structure, morphology, and thermoelectric properties of the films were analyzed. Bi
x
Sb2−x
Te
y
thermoelectric films prepared under different potential ranges all possessed a smooth morphology. After annealing treatment
at 200°C under N2 protection for 4 h, all deposited films showed p-type semiconductor properties, and their resistances all decreased to 0.04 Ω to 0.05 Ω. The Bi0.49Sb1.53Te2.98 thermoelectric film, which most closely approaches the stoichiometry of Bi0.5Sb1.5Te3, possessed the highest Seebeck coefficient (85 μV/K) and can be obtained under potentials of −200 mV to −400 mV. 相似文献
15.
A novel phase change memory with recessed cell structure has been successfully fabricated based on 40 nm Complementary-Metal-Oxide-Semiconductor technology. Etching back (EB) process and deposition-etching-deposition (DED) process are used for the formation of recessed hole and the gap filling of the recessed hole with Ge2Sb2Te5, respectively. With the combination of EB and DED processes, the recessed cell structure can be easily manufactured based on the current planar structure. The RESET current is reduced by 33.3% to 0.8 mA and the distribution tail of RESET resistance is solved. Moreover, about 107 cycles endurance with more than 300x resistance ratio have been obtained. 相似文献
16.
Jae-Hong Lim Mi Yeong Park Dong Chan Lim Bongyoung Yoo Jung-Ho Lee Nosang V. Myung Kyu Hwan Lee 《Journal of Electronic Materials》2011,40(5):1321-1325
Thermoelectric Sb
x
Te
y
films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different concentrations
of TeO2. Stoichiometric Sb
x
Te
y
films were obtained by applying a voltage of −0.15 V versus saturated calomel electrode (SCE) using a solution consisting
of 2.4 mM TeO2, 0.8 mM Sb2O3, 33 mM tartaric acid, and 1 M HNO3. The nearly stoichiometric Sb2Te3 films had a rhombohedral structure, R[`3]m R\bar{3}m , with a preferred orientation along the (015) direction. The films had hole concentration of 5.8 × 1018/cm3 and exhibited mobility of 54.8 cm2/Vs. A more negative potential resulted in higher Sb content in the deposited Sb
x
Te
y
films. Furthermore, it was observed that the hole concentration and mobility decreased with increasingly negative deposition
potential, and eventually showed insulating properties, possibly due to increased defect formation. The absolute value of
the Seebeck coefficient of the as-deposited Sb2Te3 thin film at room temperature was 118 μV/K. 相似文献
17.
Tianbao Chen Ping Fan Zhuanghao Zheng Dongping Zhang Xingmin Cai Guangxing Liang Zhaokun Cai 《Journal of Electronic Materials》2012,41(4):679-683
Antimony and tellurium were deposited on BK7 glass using direct-current magnetron and radiofrequency magnetron cosputtering.
Antimony telluride thermoelectric thin films were synthesized with a heated substrate. The effects of substrate temperature
on the structure, surface morphology, and thermoelectric properties of the thin films were investigated. X-ray diffraction
patterns revealed that the thin films were well crystallized. c-Axis preferred orientation was observed in thin films deposited above 250°C. Scanning electron microscopy images showed hexagonal
crystallites and crystal grains of around 500 nm in thin film fabricated at 250°C. Energy-dispersive spectroscopy indicated
that a temperature of 250°C resulted in stoichiometric Sb2Te3. Sb2Te3 thin film deposited at room temperature exhibited the maximum Seebeck coefficient of 190 μV/K and the lowest power factor (PF), S
2
σ, of 8.75 × 10−5 W/mK2. When the substrate temperature was 250°C, the PF increased to its highest value of 3.26 × 10−3 W/mK2. The electrical conductivity and Seebeck coefficient of the thin film were 2.66 × 105 S/m and 113 μV/K, respectively. 相似文献
18.
I. S. Virt T. P. Shkumbatyuk I. V. Kurilo I. O. Rudyi T. Ye. Lopatinskyi L. F. Linnik V. V. Tetyorkin A. G. Phedorov 《Semiconductors》2010,44(4):544-549
Bi2Te3 and Sb2Te3 films were obtained by pulsed laser ablation. The films were deposited in vacuum (1 × 10−5 Torr) on single crystal substrates of Al2O3 (0001), BaF2 (111), and fresh cleavages of KCl or NaCl (001) heated to 453–523 K. The films were 10–1500 nm thick. The structures of the
bulk material of targets and films were studied by X-ray diffractometry and transmission high-energy electron diffraction,
respectively. Electrical properties of the films were measured in the temperature range of 77–300 K. It is shown that the
films possess semiconductor properties. Several activation portions are observed in the temperature dependences of resistivity;
the energies of activation portions depend on the film thickness and crystallite size. 相似文献
19.
Virginie Richoux Sebastien Diliberto Clotilde Boulanger 《Journal of Electronic Materials》2010,39(9):1914-1919
Bismuth antimony telluride (Bi1−x
Sb
x
)2Te3 thermoelectric compounds were synthesized by pulse plating. Due to the large number of parameters available (pulse waveform,
on/off pulse time, applied current density), this advanced form of electrodeposition allows better control of the interfacial
supply and electrochemical reactions and offers effective ways to improve macroscopic properties such as adhesion and to produce
crack-free hard deposits and fine-grained films with higher uniformity and lower porosity. The influence of pulse parameters
(pulse time t
on, cathodic current density J
c) on the stoichiometry, roughness, and crystallography of deposits was studied. The thermoelectric properties (electrical
resistivity and Seebeck coefficient) of the films were measured. The results revealed that deposits have p-type conductivity directly after electroplating (Seebeck coefficient around 150 μV K−1), in contrast to films synthesized by direct current, which require annealing. An improvement of resistivity was observed:
for a direct-current-deposited film the resistivity is around 5000 μΩ m, whereas for a pulse-deposited film the resistivity was around 200 μΩ m. 相似文献
20.
Rui Lan Rie Endo Masashi Kuwahara Yoshinao Kobayashi Masahiro Susa 《Journal of Electronic Materials》2018,47(6):3184-3188
Ge2Sb2Te5 alloy has drawn much attention due to its application in phase-change random-access memory and potential as a thermoelectric material. Electrical and thermal conductivity are important material properties in both applications. The aim of this work is to investigate the temperature dependence of the electrical and thermal conductivity of Ge2Sb2Te5 alloy and discuss the thermal conduction mechanism. The electrical resistivity and thermal conductivity of Ge2Sb2Te5 alloy were measured from room temperature to 823 K by four-terminal and hot-strip method, respectively. With increasing temperature, the electrical resistivity increased while the thermal conductivity first decreased up to about 600 K then increased. The electronic component of the thermal conductivity was calculated from the Wiedemann–Franz law using the resistivity results. At room temperature, Ge2Sb2Te5 alloy has large electronic thermal conductivity and low lattice thermal conductivity. Bipolar diffusion contributes more to the thermal conductivity with increasing temperature. The special crystallographic structure of Ge2Sb2Te5 alloy accounts for the thermal conduction mechanism. 相似文献