现场STM针尖诱导Ag(111)表面局域刻蚀

本文报道用现场扫描隧道显微镜技术（in-situ STM)研究Ag(111）电极表面局域刻蚀。实验表明,STM针尖可以诱导有I^- 特性吸附的Ag(111)电极在其电化学稳定区发生表面局域刻蚀,刻蚀的发生与程度与针尖电位,样品电位及偏压等因素有紧密关系,刻蚀速度在偏压最小时达最大,刻蚀的发生也间接反映了电化学体系中的多重隧穿途径及其随电极电位的变化。     

STM研究Si(111)7×7表面畴界结构

根据对Ｓｉ（１１１）表面各种不同畴界的研究，我们发现并提出了在畴界形成过程中决定这些畴界结构的三个重要因素：二聚体（ｄｉｍｅｒ）和顶戴原子（ａｄａｔｏｍ，亦称吸附原子）之间的相互作用；７×７单胞中层错半单元（ｆａｕｌｔｅｄｈａｌｆ）和非层错半单元（ｕｎｆａｕｌｔｅｄｈａｌｆ）的差异；亚稳态的（２ｎ＋１）×（２ｎ＋１）结构的影响。     

C60在Ag(111)表面的STM图像理论模拟

本文利用离散变分和局域密度泛函（ＤＶ－ＬＤＦ）方法,通过计算Ｃ６０／Ａｇ（１１１）的电荷密度分布图,即模拟出该体系的ＳＴＭ图像,并详细地研究了体系的电子结构,结果表明,该体系中有２．３２ｅ自金属表面Ａｇ原子向Ｃ６０转移。外电场的极性对图像影响委 正偏压情形,ＬＵＭＯ电荷密度分布图为三个五边形围成则呈三叶状,反映的是体系中吸附分子的对称性,且隧道电流主要来自单键。而ＨＯＭＯ电荷密度分布图具有三重对称     

内嵌金属富勒烯Gd@C_(82)在Cu(111)和Pt(111)表面吸附结构的STM研究CSCD

利用扫描隧道显微镜(STM)研究分析了内嵌金属富勒烯分子Gd@C82在Cu(111)和Pt(111)上的低温(200～250 K)生长方式和吸附结构。不同强弱的分子-衬底间相互作用导致Gd@C82在Cu(111)和Pt(111)上的生长方式有很大区别。经过热处理后,Gd@C82分子诱导Cu(111)衬底发生重构,而在Pt(111)上未发现此现象。两种金属衬底不同的晶格常数和电子性质导致退火后的分子自组装结构也不一样:Gd@C82在Cu(111)上形成等价的两种吸附结构,即(√19×√19)R23.4°和(√19×√19)R36.6°;分子在Pt(111)上形成一种与〈110〉方向一致的密堆积结构。     

金纳米棒在Au(111)表面上的分散与STM表征

本文报道了金纳米棒的合成、在Au(111)表面上的分散、有机污染物清洗以及STM形貌表征工作.金纳米棒通过金晶种在金生长液中的选择性生长来制备.通过对金纳米棒和Au(111)表面进行修饰,利用涂层外端基团之间的静电相吸作用,把金纳米棒经由点滴法均匀地吸附在Au(111)表面上,且分散密度可通过点滴次数加以控制.本文进一...     

Si(111)湿法腐蚀后表面形态的FTIR研究

运用偏振衰减全反射傅立叶变换红外光谱技术 (ATR-FTIR) ,研究了 Si(1 1 1 )在不同比例的 NH4F-HCl溶液中腐蚀后的表面形态。通过分析表面振动模型的偏振波长及红外粗糙因子 ,表明在较低的 PH值的NH4F-HCl溶液中腐蚀的 Si(1 1 1 )表面粗糙度较大 ,与通过扫描隧道显微镜 (STM)技术测量的结果基本一致     

用STM在Si(111)7×7表面进行“有序移植”

我们用ＳＴＭ在低压大电流条件下对Ｓｉ（１１１）７×７表面进行了原子操纵研究，这种方法即可从表面提出原子而形成沟槽结构，又可将提出的原子重新植入样品表面形成一维凸起，在样品表面形成有序排列，从而成功地实现了对原子群体的“有序移植”     

C_(90)分子单层膜在Au(111)表面的STM研究

在超高真空中使用热蒸发方法,在Au(111)表面上制备了C90分子的分子单层膜,并利用超高真空低温扫描隧道显微镜在120 K温度下对其结构进行研究。观察到C90分子在Au(111)表面上先是沿着台阶边缘生长,分子铺满一层后,会在薄膜上形成岛状结构。本文对岛状结构进行了原位高分辨表征,观察到C90分子在正偏压和负偏压下的几种不同形貌,并给出了各种形貌所对应的C90分子构型。     

C90分子单层膜在Au(111)表面的STM研究

在超高真空中使用热蒸发方法,在Au(111)表面上制备了C90分子的分子单层膜,并利用超高真空低温扫描隧道显微镜在120 K温度下对其结构进行研究.观察到C90分子在Au(111)表面上先是沿着台阶边缘生长,分子铺满一层后,会在薄膜上形成岛状结构.本文对岛状结构进行了原位高分辨表征,观察到C90分子在正偏压和负偏压下的...     

Incorporation of Sn on GaAs (111)A substrates by molecular beam epitaty

Behavior of Sn as donor species in the MBE growth of GaAs on (111)A substrates has been investigated by varying the growth temperature from 460 to 620°C, As₄:Ga flux ratio from 4 to 25, and Sn concentration from 10¹⁶ to 10²⁰ atoms cm^-3. Secondary ion mass microscopy measurements show that Sn does not surface segregate on (111)A substrates under this growth condition, in contrast to that on (001) substrates. Sn is uniformly incorporated throughout the bulk of the grown layer for all samples, apart from the most highly doped ones. To increase the Sn carrier concentration on the (111)A substrates, the measured carrier concentration shows that doping should be carried out at a low growth temperature and/or high As₄:Ga flux ratio.     

Sn3.8Ag0.7Cu和Sn37Pb焊点界面显微结构研究

利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究了Sn3.8Ag0.7Cu（Sn37Pb）/Cu焊点在时效过程中的界面金属间化合物（IMC）形貌和成份。结果表明：150℃高温时效50、100、200、500h后,Sn3.8Ag0.7Cu（Sn37Pb）/Cu焊点界面IMC尺寸和厚度增加明显,IMC颗粒间的沟槽越来越小。50h时效后界面出现双层IMC结构,靠近焊料的上层为Cu6Sn5,邻近基板的下层为Cu3Sn。之后利用透射电镜观察了Sn37Pb/Ni和Sn3.8Ag0.7Cu/Ni样品焊点界面,结果显示,焊点界面清晰,IMC晶粒明显。     

The Growth of Transition Metals on H‐Passivated Si(111) Substrates

The growth of Co and Ag layers on wet‐processed H‐passivated Si(111) substrates by molecular beam epitaxy (MBE) has been studied using high resolution scanning tunneling microscopy (STM) with regard to possible applications of the layers in magnetoelectronic devices. Roughness and intermixing at interfaces as functions of deposition temperature and layer thickness are key parameters for the performance of such devices. The initial growth of Co and Ag and the influence of Ag atoms on the Si(111) surface reconstructions provide insight into adatom–substrate interactions.     

Solid-state annealing behavior of two high-Pb solders, 95Pb5Sn and 90Pb10Sn,on Cu under bump metallurgy

The solid-state annealing behavior of two high-lead solders, 95Pb5Sn and 90Pb10Sn (in wt.%), was examined. After reflow, Cu₃Sn intermetallics formed on the Cu under bump metallurgy (UBM) for both solder alloys. However, solidstate annealing produced significantly different reaction morphologies for the two solder compositions. The Cu₃Sn intermetallics spalled off faster at higher temperatures in the 95Pb5Sn solder. In the case of 90Pb10Sn solder, the Cu₃Sn intermetallics continued to grow even after 1500 h at 170°C. The difference was explained by a two-step phenomenon—Sn diffusion from the bulk solder region to the solder/Cu₃Sn interface (J_Sn), and subsequent intermetallic formation (I_Cu3Sn) by interdiffusion of Cu and Sn. For 95Pb5Sn, the relation, J_Sn < I_Cu3Sn was postulated because of insufficient supply of Sn. The relation, J_Sn > I_Cu3Sn was suggested for the continuous intermetallic growth of the 90Pb10Sn solder. Although a small difference was expected between the two quantities in both solder alloys, the difference in the solid-state annealing behavior was dramatic.     

Effect of Cu additives on Sn whisker formation of Sn(Cu) finishes

Sn whisker formation on Sn(Cu) finishes has been studied. (1) With respect to the thickness effect, we found that Sn whisker density for pure Sn and Sn0.7Cu finishes has a linear relationship with the finish thickness. The safety thickness for Sn and Sn0.7Cu finishes is about 10 μm and 20 μm, respectively. (2) With respect to the alloying effect, we found that Sn whisker formation could be retarded by increasing Cu content in the Sn(Cu) finishes. We conclude that the Cu additives could reduce the two major driving forces of the Sn whisker formation, i.e., metal underlayer dissolution and thermal stress. The Cu additives self-formed a Cu-Sn compound barrier layer, which effectively prevents the reaction and dissolution with the metal underlayer. On the other hand, the Cu additives precipitated out as Cu-Sn compound in the Sn(Cu) finish layer, which is believed to be the reason for smaller values of the coefficient of thermal expansion (CTE) for Sn(Cu) alloys. The smaller CTE values results in a lower thermal stress level in the Sn(Cu) finishes.     

电迁移对Sn3.0Ag0.5Cu无铅焊点剪切强度的影响

通过热风回流焊制备了Cu/Sn3.0Ag0.5Cu/Cu对接互连焊点,测试了未通电及6.5 A直流电下通电36 h和48 h后焊点的剪切强度.结果表明,电迁移显著地降低了焊点的剪切强度,电迁移36 h使剪切抗力降低约30%,电迁移48 h降低约50%.SEM观察断口和界面形貌表明,界面金属间化合物增厚使断裂由韧性向脆性...     

时效对Sn3.0Cu0.15Ni/Cu界面组织的影响

研究了150℃时效0,200,500h对Sn3.0Cu0.15Ni/Cu界面组织结构的影响.结果表明:界面金属间化合物层由Cu6Sn5层和Cu3Sn层组成,质量分数为0.15％的Ni的加入会使IMC层最初变厚,但在时效过程中,热稳定性强的界面化合物(Cu,Ni)6Sn5的生成,会抑制Cu3Sn化合物层的生长;同时Ni的加入会降低Cu6Sn5颗粒的长大速度,并且随着时效时间的延长,Cu6Sn5颗粒的形貌呈多面体结构.