混晶（RbxK1—x）2SnCl6的相变研究

用非极性喇曼散射光谱研究了混晶（ＲｂｘＫ１－ｘ）２ＳｎＣｌ６性质随组份（０〈ｘ〈１）及温度（１０Ｋ〈Ｔ〈３００Ｋ）的变化，发现在纯Ｋ２ＳｎＣｌ６晶体中用Ｒｂ＾＋部分替代Ｋ＾＋后，将降低原Ｋ２ＳｎＣｌ６的相变温度Ｔｃｌ。当混晶中Ｒｂ＾＋成份超过极限浓度（ｘ〉０．７）后，该相变就被抑制，不同组份样品的同一喇曼模频率，随Ｒｂ＾＋的增加，向低频方向移动，用平均力常数拟合给出很好的理论解释。     

〔（NH_4）_xK_（1－x）〕_2SnCl_6混晶的喇曼散射研究

本文用喇曼散射的方法研究了六氯锡化钾铵混晶系列样品［（ＮＮ_４）_ｘＫ_（１－ｘ）］_２ＳｎＣｌ_５（ｘ＝０，０．０５，０．１，０．１５，０．２，０．２５，０，３，１）从室温到７７Ｋ的行为，首先观察到了其外振动模的双模行为，并且还发现了其一内模Ｔ_（２ｇｉｎｔ）的宽度随铵离子浓度ｘ的增加而增加，相变温度Ｔｃ却随铵离子浓度的增加而迅速下降，下降速率约为ｄＴ_ｃ／ｄｘ＝－６００Ｋ／ｍｏｌ，这一行为是由于正四面体的ＮＨ_４￣＋离子对正八面体的ＳｎＣｌ_６￣（２－）离子团的转动产生阻碍而引起。内模Ｔ_（２ｇｉｎｔ）的宽度变化也是由于铵离子的转动影响以及由它引起的晶格畸变所导致。双模行为来自于强烈的集团效应。     

稀磁半导体Zn_（1－x）Mn_xSe外延膜的反射和光致发光谱

测量了用热壁外延（ＨＷＥ）生长的不同组分（０≤ｘ≤０．９８）的Ｚｎ１－ｘＭｎｘＳｅ薄膜在温度为３００Ｋ下的反射光谱，用Ｘ射线能借测定样品实际的组分ｘ值，由此获得了其能隙Ｅｇ与组分ｘ的关系：在Ｏ＜Ｘ＜０．２组分范围，Ｅｇ随ｘ的变化显示了反常现象，当Ｘ＞０．２时，能隙Ｅｇ随ｘ线性增大。在室温和低温下测量了样品的光致发光，除观测到Ｍｎ２＋离子内部４Ｔ１→６Ａ１发光峰外，在其低能边观测到一个较宽的发光峰，对结果进行了分析讨论。     

THE SUPERCONDUCTIVITY IN Al-DOPEDY_(1-x)Al_xBa_2Cu_3O_y

本文系统地分析了在Ｙ１－ｘＡｌｘＢａ２Ｃｕ３Ｏｙ（ｘ＝０～０．７）中用Ａｌ替代Ｙ的替代效应．我们发现当ｘ＜０．４时，Ａｌ主要替代在Ｙ位，引起结构畸变，从而导致氧含量的减少和Ｏ－Ｔ相变，转变温度随Ａｌ含量增加而下降．当掺杂量大于０．４，Ａｌ开始占据Ｃｕ（１）和Ｃｕ（２）位，样品变为四方结构，Ｔｃ迅速下降．ＸＰＳ分析表明，Ａｌ的位置依赖于掺杂量，随掺杂浓度的增加Ａｌ依次替代Ｙ，Ｃｕ（１），Ｃｕ（２）．同时我们观察到Ｔｃ和ＣｕＯ２平面间相互作用的正比关系．     

半磁半导体Zn_（1－x）Mn_xS中的能量传递

本文测量了Ｚｎ１－ｘＭｎｘＳ在不同Ｍｎ浓度（０．００１＜ｘ＜０．５）下的发射谱和衰减曲线，并且用Ｙｏｋｏｔａ和Ｔａｎｉｍｏｔｏ模型进行了分析在对４Ｔ１衰减曲线进行拟合时发现衰减曲线是两种不同弛豫过程之和：（１）孤立的Ｍｎ２－离子的４Ｔ１衰减，它确定衰减曲线的尾部，有较长的衰减寿命；（２）Ｍｎ２－离子聚集体（例如Ｍｎ２－离子对）的４Ｔ１衰减，这种衰减比单个Ｍｎ２－离子的衰减更快．我们深入分析了在ｘ＝０．０６２，Ｔ＝８０Ｋ时的Ｚｎ１－ｘＭｎｘＳ的发射谱及其衰减曲线，得到两个衰减寿命：τ１＝７０μｓ，τ２＞１０００μｓ，这表明在高Ｍｎ浓度时存在着两个弛豫过程：一个是较快的，另一个则是较慢的，根据Ｇｏｅｄｅ等人的实验结果可以断定较慢的过程来自孤立的Ｍｎ２－离子，那么便可以判知较快的过程是来源于Ｍｎ２－离子对．正是高Ｍｎ浓度下的Ｚｎ１－ｘＭｎｘＳ中存在着Ｍｎ２＋－Ｍｎ２＋离子对，在其间有能量迁移以及它和能量受主之间的能量传递造成了该体系中的ＩＲ发射．     

Bi_（2．2）Sr_（1．8）Ca_（1．05）Cu（2．15－x）NaxO_

本文介绍了用熔融法制备Ｂｉ２．２Ｓｒ１．８Ｃａ１．０５Ｃｕ２．１５－ｘＮａｘＯ８＋ｙ（ｘ＝０，０．４～０．８）样品，发现诸样品零电阻温度都在９０Ｋ左右，其小ｘ＝０．７．Ｔｃ０达到９２，５Ｋ．在８１Ｋ较高温区，该类样品仍然表现出良好的超导电性，其临界电流密度还达到１０３Ａ／ｃｍ２量级．     

低补偿度n－Hg＿（1－x）Cd＿xTe的磁致金属－绝缘体相变和相变后的温度激活输运行为

报道了ｘ＝０．２１４组份、低补偿度（Ｋ《１）ｎ－Ｈｇ＿（１－ｘ）Ｃｄ＿ｘＴｅ晶体在０．３─３０Ｋ温度范围，０─７Ｔ强磁场下的横向磁阻、电子霍耳迁移率、霍耳系数测量结果，观测到了磁致金属－绝缘体相变和相变后的温度激活输运行为。分析实验数据，提出：低补偿度、组份：ｘ＝０．２附近的ｎ－Ｈｇ＿（１－ｘ）Ｃｄ＿ｘＴｅ，磁致金属－绝缘体相变（ＭＩＴ）发生的机理是载流子在浅施主杂质态上的磁冻结；发生磁冻结的前提是热冻出（ｔｈｅｒｍａｌｆｒｅｅｚｅ－ｏｕｔ），即首先必须在很低的温度下将导带电子冻出到施主态上。相变后的温度激活输运行为可以表示成Ｒ＿Ｈ（Ｔ）＝Ｒ＿（Ｈ０）ｅｘｐ［ａ／ｋＴ］，它实际上反映了磁冻结在施主上的电子，随温度的升高，逐步热激发到导带的过程，从磁致ＭＩＴ后的激活能初步推知，导带下存在两个浅施主能级。     

Gd＿（1－x）Ca＿xBa＿2Cu＿3O＿（7－y）高温超导体压力效应的研究

研究了Ｇｄ＿（１－ｘ）Ｃａ＿ｘＢａ＿２Ｃｕ＿３Ｏ＿（７－ｙ）（０．０≤Ｘ≤０．２０）高温超导体在常压和高压下的超导电性在１－３００Ｋ温度范围内，利用Ｂｒｉｄｇｍａｎ对顶砧获得压力达９．０ＧＰａ，测量了（Ｘ＝０．１０，０．１５，０．２０）样品的ｄＴ＿ｃ／ｄｐ分别为７．６８，７．８和４．４６Ｋ／ＧＰａ。发现Ｔ＿ｃ的压力导数随着ｃａ￣（２＋）含量的增加而下降，分析了氧含量对Ｔ＿ｃ和ｄＴ＿ｃ／ｄＰ的影响．利用常压下晶格参数精修值和阳离子与氧离子间距随压力的改变，说明ＣｕＯ＿２面在超导电性上的作用，用ＣｕＯ＿２面之间耦合解释Ｔ＿ｃ（Ｐ）曲线的非线性关系。     

高Tc超导体YBaCuO（F）：磁性和ESR测量

本研究高Ｔｃ大块超导体ＹＢａ２Ｃｕ３Ｏ７－ｂ（Ｆｘ）（其中ｘ＝０．０，０．５，０．７５，１．０，１．５，２．０，２．５）的磁性。Ｘ射线衍射实验表明相当多的Ｆ进入了ＹＢａＣｕＯ（１２３）晶格并被Ｏ空位俘获。用振动样品磁强计（ＶＳＷ）测试这些样品的质量比磁矩σ与温度Ｔ的关系，以及抗磁性磁滞回线。未掺氟样品的Ｔｃ为８９Ｋ，掺Ｆ（ｘ＝０．７５）的样品具有最高的Ｔｃ０＝９３Ｋ和最强的抗磁性。在１５０Ｋ样品     

Y_（1－x）Pr_xBa_2Cu_3O_（7－δ）超导体正常态异常的正电子湮没

在７７—３００Ｋ温度范围内用正电子湮没方法测量了Ｙ１－ｘＰｒｘＢａ２Ｃｕ３Ｏ７－δ（ｘ＝０．２，０．１，０．０）三个超导样品中正电子湮没寿命随温度的变化，细致地研究了正常志异常现象．Ｘ为０．０和０．１的二个样品分别在较Ｔｃ高４０Ｋ和３０Ｋ处观察到了正常态异常现象ｘ＝０．２样品（Ｔｃ＜８０Ｋ）没有观察到正常态异常现象．实验观察到的正常态异常现象可能是发生超导转变的前奏，由结构不稳定产生的类相交所致．     

Adsorption structure and work function of dicarboxylic acid on Cu(1 1 0) surface

We investigated the relation between work function and the adsorption structure of dicarboxylic acids (organic molecules) such as succinic acid (HOOC-CH₂-CH₂-COOH) and an adipic acid (HOOC-(CH₂)₄-COOH) on a Cu(1 1 0) surface (electrode) as a function of the surface temperature using a Kelvin probe (KP). The work function changes of the two acids are similar. The work function increases by adsorption at room temperature due to ionization of molecules and then decreases with increasing temperature until 450 K due to the effects of change in the dipole moment of the conformational change of the molecule. From 450 to 600 K, the work function is constant because of competition between desorption and change in the dipole moment of molecules. It then reached the clean-surface value. Experiments clarified that the work function was affected by the adsorbed difference in conformation of molecules.     

Growth of Rh nanoclusters on TiO2(1 1 0): XPS and LEIS studies

Rhodium clusters were prepared by evaporation on a nearly stoichiometric TiO₂(1 1 0) surface. The growth of metal nanoparticles, as a function of rhodium coverage, could be followed by monitoring the Rh 3d_5/2 XP peak position and by low energy ion scattering spectroscopy (LEIS). The substrate temperature in the 160-300 K regime during evaporation significantly influences the cluster size, leading to smaller crystallites at low temperature. Annealing the surface results in the agglomeration of rhodium, which commenced at lower temperature for smaller clusters. At high temperatures (∼900 K) encapsulation of rhodium also occurred.     

Proton NMR T 1 Studies in Methylammonium TrichlorO Stannate(II) (CH 3 NH 3 SnCl 3 )

Proton spin lattice relaxation time ( T 1 ) measurements have been carried out in methylammonium trichloro stannate(II) (CH 3 NH 3 SnCl 3 ) as a function of temperature in the range 317-5 K at a Larmor frequency of 10 MHz. The temperature dependence of T 1 shows a phase transition around 220 K and four T 1 minima (294 K, 62 K, 32 K and 12 K). The results are discussed in terms of proton dynamics, namely, uncorrelated reorientation of NH 3 and CH 3 groups at high temperatures and tunnelling of NH 3 and CH 3 protons at low temperatures.     

Vanadium nanoclusters on Si(1 1 1) 7 × 7 surface studied by scanning tunneling microscopy

The size distribution and shape transition of self-assembled vanadium silicide clusters on Si(1 1 1) 7 × 7 have been investigated by scanning tunneling microscopy. Nanoclusters were formed by submonolayer vanadium deposition at room temperature followed by subsequent annealing (solid phase epitaxy - SPE). At room temperature, initially V-nanoclusters are formed which occupy sites avoiding the corner hole parts of the unit cells in the Si(1 1 1) 7 × 7 surface. Upon annealing, strong metal-silicon reaction occur leading to the formation of vanadium silicide nanoclusters. As a function of temperature, both, flat (2D) and three dimensional (3D) clusters have been obtained. After annealing at temperatures around 900 K many faceted clusters are created, whereas at higher annealing temperature, around 1300 K, predominantly 3D clusters are formed. The size distribution of SPE grown clusters could be well controlled in the range of 3-10 nm. The cluster size depends on the annealing temperature as well as on the initial vanadium coverage. Based on high resolution STM images a structure model for one kind of vanadium disilicide clusters exposing atomically flat surfaces was proposed.     

Direct observation of the formation of polar nanoregions in Pb(Mg1/3Nb2/3)O3 using neutron pair distribution function analysis

Using neutron pair distribution function analysis over the temperature range from 1000 to 15 K, we demonstrate the existence of local polarization and the formation of medium-range, polar nanoregions (PNRs) with local rhombohedral order in a prototypical relaxor ferroelectric Pb(Mg(1/3)Nb(2/3))O3. We estimate the volume fraction of the PNRs as a function of temperature and show that this fraction steadily increases from 0% to a maximum of approximately 30% as the temperature decreases from 650 to 15 K. Below T approximately 200 K the volume fraction of the PNRs becomes significant, and PNRs freeze into the spin-glass-like state.     

Adsorption of oxygen on W(100): Adsorption kinetics and structure

The adsorption of oxygen on W(100) single crystal surfaces is studied by Auger electron spectroscopy (AES), flash desorption, low-energy electron diffraction (LEED) and retarding field work function measurements with the aim of obtaining a better understanding of the adsorption kinetics and of the structures of the adsorbed layer. The AES results reveal step-wise changes of the sticking coefficients in the coverage range 0 to 1, and activated adsorption at higher coverages. Upon room temperature adsorption a series of complex LEED patterns is observed. In layers adsorbed at 1050 K and cooled to room temperature, the well-known p(2 × 1) structure is the first ordered structure observed. This structure shows a reversible order-disorder transition between 700 K and 1000 K and is characterized by a work function which is lower than that of the clean surface. Heating room temperature adsorbates changes their structure irreversibly. At temperatures below 750 K some new structures are observed. Combining the results obtained in this study with other published work leads to a considerable revision of the previously accepted model of the adsorption of oxygen on W(100).     

Structural and morphological evolution of Co on faceted Pt/W(1 1 1) surface upon thermal annealing

The structural and morphological changes of a 1.1 monolayer (ML) Pt deposit on W(1 1 1) have been investigated in situ, in ultra-high vacuum, as a function of the annealing temperature from 700 to 1340 K, by a combination of grazing incidence X-ray diffraction and grazing incidence small-angle X-ray scattering. Before annealing, the thin Pt layer is two-dimensional and lattice-matched to the W(1 1 1) surface. The faceting of Pt/W(1 1 1) towards nanoscale three-sided pyramids with {2 1 1} facets has been detected from 715 K. At this stage, the pyramids, which have a 5-nm average lateral size, cover nearly perfectly the surface. At higher temperatures, they increase in size. The role of the edge energy in the nanofaceting process is discussed. In addition, 4 MLs Co are deposited at room temperature on the smallest Pt/W pyramids. The obtained three-dimensional Co islands are correlated with the Pt/W nanopyramids and Co is relaxed on Pt/W. At approximately 800 K, a CoPt alloy is formed and becomes better ordered as the annealing temperature increases. At 1100 K, both defaceting and phase separation begin; the CoPt alloy segregates on the W(1 1 1) flat surface, while Co forms an epitaxial layer on the {2 1 1} facets. In addition, in the temperature range of 1100-1200 K, a great majority of {2 1 1} large facets coexist with some {1 1 0} small facets. Finally, the surface becomes flat again at 1250 K.     

Dy substitution effect on the temperature dependences of magnetostriction in Pr_(1-x)Dy_xFe_(1.9) alloys

The temperature dependences of magnetostriction in Pr_(1 x)Dy_xFe_(1.9)(0 ≤ x ≤ 1.0) alloys between 5 K and 300 K were investigated.An unusual decrease of magnetostriction with temperature decreasing was found in Pr-rich alloys(0 ≤x≤ 0.2),due to the change of the easy magnetization direction(EMD).Dy substitution reduces the magnetostriction in high-magnetic field(10 kOe ≤ H≤90 kOe) at 5 K,while a small amount of Dy substitution(x = 0.05) is beneficial to increasing the magnetostriction in low-magnetic field between 10 K and 50 K.This makes the alloys a potential candidate for low temperature applications.     

In-situ study on thermal decomposition of 1,3-disilabutane to silicon carbide on Si(1 0 0) surface

The intermediates of thermal decomposition of 1,3-disilabutane (SiH₃CH₂SiH₂CH₃, DSB) to form SiC on Si(1 0 0) surface were in situ investigated by reactive ion scattering (RIS), temperature programmed reactive ion scattering (TPRIS), temperature programmed desorption (TPD), and auger electron spectroscopy (AES). DSB as a single molecular precursor was exposed on Si(1 0 0) surface at a low temperature less than 100 K, and then the substrate was heated up to 1000 K. RIS, TPD, and AES investigations showed that DSB adsorbed molecularly and decomposed to SiC via some intermediates on Si(1 0 0) surface as substrate temperature increasing. Between 117 and 150 K molecularly adsorbed DSB desorbed partially and decomposed to CH₄Si₂, which is the first observation on Si(1 0 0) surface, and further decomposed to CH₄Si between 150 and 900 K. CH₄Si lost hydrogen and formed SiC over 900 K.     

Low temperature InSb(0 0 1) surface structure studied by scanning tunneling microscopy

InSb(0 0 1) surface prepared by ion sputtering and thermal annealing has been studied in the temperature range from 77 K up to 300 K using scanning tunneling microscopy (STM). At 300 K the surface is c(8 × 2) reconstructed as indicated by low energy electron diffraction and STM images, and its structure appears to be consistent with the “ζ-model” recently proposed for this surface. Upon lowering of the temperature below 180 K a new phase appears on the surface. This phase is characterized by the surface structure period doubling along [1 1 0], lowering the surface symmetry from c2mm to p2, and appearance of structural domains. Possible origins of the new phase are discussed.