Si doping in Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript> film to reduce the writing current of phase change memory

The characteristics of phase change memory devices in size of several micrometers and with pure Ge₂Sb₂Te₅ (GST), N-doped GST, and Si-doped GST films were investigated and compared with each other. The Si-doped GST device can perform SET and RESET cycles, even if the Si dopant is as small as 4.1 at. %. But the GST and N-doped GST device cannot perform the RESET process, though the SET state resistance of N-doped device is almost the same as that of Si-doped device and larger than that of GST device. In order to explain this phenomenon, the electrical and DSC characteristics of three kinds of films were investigated. Phase separation was found in Si-doped GST films. The reason of the RESET ability of Si-doped GST devices is supposed to be the existence of rich Si phases which act as micro-heaters. Thermal conduction simulations confirmed this supposition and indicate that the separated high resistance phase (rich Si phase) can heat the active volume of device efficiently and reduce the writing current largely. PACS 71.55.Gs; 71.55.Jv; 74.81.Bd; 85.30-z     

宽带源系统中反射相移对BGOCS影响的理论分析

提出了适用于采用具有一定谱宽光源的BGOCT的理论分析方法,对不同光源谱宽通过反射相移的色散对系统输出的影响进行了理论研究.结果表明,光源谱宽在60 nm范围内,宽带系统输出相对单色系统输出变化小于万分之二.在理论研究中若不考虑光源线宽对其他光学参量的影响时,用单色光模型处理宽带系统的做法是合理的与可行的.     

Chaotic attractor transforming control of hybrid Lorenz-Chen system

Based on passive theory, this paper studies a hybrid chaotic dynamical system from the mathematics perspective to implement the control of system stabilization. According to the Jacobian matrix of the nonlinear system, the stabilization control region is gotten. The controller is designed to stabilize fast the minimum phase Lorenz-Chen chaotic system after equivalently transforming from chaotic system to passive system. The simulation results show that the system not only can be controlled at the different equilibria, but also can be transformed between the different chaotic attractors.     

The magnetic and dielectric properties of multiferroic Sr- substituted Zn2-Y hexagonal ferrites

The magnetic and dielectric properties of Sr-substituted Zn2-Y hexagonal ferrites （Ba2-x SrxZn2Fe12O22, 1.0 〈 x ≤ 1.5） are studied in this paper. Sr substitution will lead to the variation of cation occupation, which influences both the magnetic and electric properties. As Sr content x rises from 1.0 to 1.5, magnetic hysteresis loop gets wider gradually and the permeability drops rapidly due to the transformation from ferrimagnetic to antiferromagnetic phase. Moreover, permittivity rises with increasing Sr content. Under a certain external magnetic field, the phase transition of helical spin structure of Ba0.5Srl.5Zn2Fe12O22 at about 295 K seems to open a possibility for the room-temperature ferroelectricity induced by magnetic field. But its low resistivity prevents the observation of ferroelectric and magnetoelectric properties at room-temperature.     

Design of the target type flowmeter based on fiber Bragg grating and experiment

The target type flowmeter based on fiber Bragg gratings （FBGs） is experimentally studied. The relationship between the central wavelength shift of FBG and the flux is derived and the analytic expression is also given. Simulation and preliminary experiments have been carried out, and experimental validation of the water further proves the feasibility of the sensor. The experimental results verify the proposed sensor which can measure flux range from 200 to 1200 cm^3/s. And on this basis, the improvement program is raised.     

Porous polymer films and honeycomb structures based on amphiphilic dendronized block copolymers

Fabrication of honeycomb patterned films from our synthesized amphiphilic dendronized block copolymer by "on-solid surface spreading" method and "on-water spreading" method was reported for the first time in this paper. The comparison of the two methods indicated honeycomb-patterned films with smaller size, and larger surface density of micropores can be fabricated by spreading on water but with lower regular arrangement. Furthermore, several influencing factors on the formation of the honeycomb structure and the different morphologies, such as the concentration of the copolymer solution and the relative humidity in the atmosphere and the substrates, were investigated. The results showed that comparably high relative humidity from 80% to 95% was needed, and the mica plate as a spreading substrate was suitable to form orderly porous films for such a copolymer. The best ordered pattern could be formed from the copolymer with concentration of 1.00 mg/mL at the relative humidity of 85% using a mica plate. Besides, strong periodicity, regularity, and a large, defect-free area were notable, which made this structure extremely interesting for applications for templated molecular objects formed via intramolecular metal or metal oxide synthesis.     

Solution route to single crystalline SnO platelets with tunable shapes

Square and round single crystalline SnO platelets have been prepared in a solution-based chemical route aided with sonication at room temperature.     

Ordered thin films of alkyloxy-substituted benzaldehydes on a graphite surface studied by scanning tunneling microscopy

The molecular assembly of three different trialkyloxy-substituted benzaldehydes on graphite has been studied using scanning tunneling microscopy (STM). It is found that these benzaldehydes, which do not have intermolecular hydrogen bonding, could form a lamella arrangement in which the headgroups are aligned side by side. The effect due to the alkyl chain length on the lamella structure is also presented. Received: 21 January 2002 / Accepted: 22 March 2002 / Published online: 10 September 2002 RID="*" ID="*"Corresponding author. Fax: +86-10/6255-7908     

Structure and thermal behaviors of organic crystals based on substituted 1,3,4-thiadiazoles

The crystalline structure of some compounds containing the 1,3,4-thiadiazole moiety, (1) 5-ethyl-2-amino-1,3,4- thiadiazole (EATZ), (2) 5-benzylsulfany-2-amino-1,3,4-thiadiazole (BSATZ) and (3) 2,5-bis-benzylsulfanyl-1,3,4-thiadiazole (BBSTZ) were determined. Both EATZ and BBSTZ show orthorhombic structures with space group Pbca and BSATZ a monoclinic system with space group C2/c. The lattice parameters: a=0.72280 (14), b=1.0811 (2), c=1.6210 (3) nm for 1, a=2.5282 (5), b=0.59083 (12), c=1.5390 (3) nm for 2 and a=0.87530 (18), b=1.0365 (2), c=3.6098 (7) nm for 3. To compare the intra- and intermolecular interactions in thiadiazole containing organic crystals, thermal analysis studies on each crystal is performed using DSC and TG in N₂ atmosphere to describe the thermal behaviors. Based on the results, the changing regularity of melting point and decomposition temperature of these compounds is educed     

A versatile approach to PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 from L-(-)-quebrachitol

[reaction: see text] A versatile synthesis of PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 is disclosed, starting from L-(-)-quebrachitol, a byproduct of latex production. The crystalline nature of most intermediates and the utilization of inexpensive protecting groups facilitate this synthetic route and its scale-up.