用HREELS研究氢在GaAs和InP的(111),()表面上的吸附

氢在GaAs和InP表面上的吸附可以用高分辨率电子能量损失谱(HREELS)来探测。Ga—H,As—H,In—H和P—H键的伸缩振动各自对应于不同的能量损失。但是As—H振动极容易和Ga—H振动追加声子损失相混淆,只有从损失峰的相对强度比较上来区别。实验得到吸附的氢与表面原子的成键情况取决于表面的原子结构及电子分布。对于GaAs(111)面,低暴露量时只形成Ga—H键,而高暴露量时还可以形成As—H键。而InP(111)表面由于是经过磷气氛退火处理的,在低暴露量下In—H与P—H键均可形成。InP(Ⅲ)面上只看到P—H损失峰,说明这个表面是完全以P原子结尾的。在(Ⅲ)面上出现小面的情形,则表面Ⅲ族和Ⅴ族原子均可同氢成键。     

用HREELS研究氢在GaAs和InP的（111），（III）表面上的吸附

氢在GaAs, 和InP 表面上的吸附可以用高分辨率电子能量损失谱(HREELS) 来探测.Ga-H侧, As-H , In-H 和P-H 键的伸缩振动各自对应于不同的能量损失. 但是A-H 振动极容易和Ga-H 振动追加声子损失相混淆, 只有从损失峰的相对强度比较上来区别。实验得到吸附的氢与表面原子的成键情况取决于表面的原子结构及电子分布. 对于GaAs (1 1 1)面, 低暴露量时只形成Ga-H 键, 而高暴露量时还可以形成As-H 键.而InP(1 1 1 ) 表面由于是经过磷气氛退火处理的, 在低暴露量下In 一H 与P一H 键均可形成. InP (III) 面上只看到P-H 损失峰, 说明这个表面是完全以P 原子结尾的. 在(1 1 1 ) 面上出现小面的情形, 则表面III族和V族原子均可同氢成键. 关键词：     

水汽在淀积金属钠的InP(111)表面的吸附

用UPS和HREELS研究室温下水汽在清洁的和淀积了金属钠的InP(111)表面的吸附。表面淀积了0.3单层金属钠之后,水汽在InP(111)表面的粘附系数显著增加,推测其原因可能与钠原子和表面的磷原子间的电荷转移有关。水汽主要以不分解的分子态形式吸附在表面。在HREELS谱中观察到与P—H键有关的282meV能量损失峰,表明部分水汽可能与淀积在表面的钠原子发生反应或者在表面发生分解。 关键词：     

AI在GaAs(110)面上的吸附

用电荷自洽的EHMO方法研究了Al在GaAs(110)面上的吸附问题。比较了两种吸附构型,从能量极小的观点定出了稳定的吸附应为Al取代表面Ga原子,使Ga落在表面As的悬挂键上。还计算了电荷转移、成键情况和状态密度。 关键词：     

H原子在Al(111)和Ag(111)面上的吸附

本文用电荷自洽的EHT方法,研究了H原子在Al(111)和Ag(111)面上的吸附,结果指出:在Al(111)面上,H以原子状态吸附在某些对称位置上,它也能渗透到表面层中去,成为填隙原子;H₂分子在表面处发生解离吸附。在Ag(111)表面上,H原子有可能以分子状态吸附,H—H键平行于表面,这与高分辨率电子能量损失谱所得到的实验结果一致;但H₂分子在Ag(111)表面也可能发生解离吸附。 关键词：     

水汽在淀积金属钠的InP()表面的吸附

用UPS和HREELS研究室温下水汽在清洁的和淀积了金属钠的InP(Ⅲ)表面的吸附。表面淀积了0.3单层金属钠之后,水汽在InP(Ⅲ)表面的粘附系数显著增加,推测其原因可能与钠原子和表面的磷原子间的电荷转移有关。水汽主要以不分解的分子态形式吸附在表面。在HREELS谱中观察到与P—H键有关的282meV能量损失峰,表明部分水汽可能与淀积在表面的钠原子发生反应或者在表面发生分解。     

Cl在GaAs(110)面上的吸附

本文主要研究Cl是吸附在GaAs(110)理想表面还是弛豫表面,是与表面正离子成键还是与表面负离子成键。计算采用集团模型和密度自洽的EHT方法。结果表明Cl只能吸附在弛豫的GaAs(110)面上,与表面As原子成键。在这个位置上吸附Cl的态密度与实验符合较好。 关键词：     

In/GaAs(111)界面形成过程的电子能谱研究

用光电子能谱结合LEED图样分析的方法研究了In在非解理的GaAs(111)面上的界面形成过程。观察到在这一过程中三维In集团的生长起支配作用。发现对于所有研究过的n型样品,包括Ga终止的GaAs(111)-A面和As终止的GaAs(111)-B面,淀积In之前的表面费密能级均在VBM上面0.75±0.05eV处,在淀积过程中迅速移至VBM上面0.90±0.05eV处。 关键词：     

室温下InP(100)表面K诱发催化氮化反应的同步辐射光电子能谱研究

利用同步辐射光电子能谱研究了室温下p型InP(100)表面,由于K吸附诱发的催化氮化反应过程。对于N_2/K/InP(100)体系的P2p;In4d芯能级和价带谱的研究表明:碱金属吸附于InP(100)表面可以强烈地影响其在室温下的氮化反应,K的存在极大地提高了N_2在InP(100)表面的粘附系数。由我们的实验结果和碱金属吸附于GaAs(110),InP(110),GaP(110)表面的研究结果可知,碱金属吸附于Ⅲ-V族半导体表面后,可以极大地提高N_2在Ⅲ-V族半导体表面的粘附系数,从而促进Ⅲ-V族半 关键词：     

金属铝在半导体表面的吸附

本文采用集团模型,用自洽的EHT方法计算金属Al在Si(111)和GaAs(110)面上吸附的稳定的几何构型和电子态,结果表明,Al在Si(111)面的三度开位上的离子吸附比顶位的共价吸附更稳定,态密度与实验符合也更好,Al吸附在GaAs(110)面上,将取代表面Ga原子,形成AlAs,此时GaAs(110)面将恢复到不弛豫的理想位置。 关键词：     

HREELS investigation of the first stage of interaction of atomic hydrogen with GaAs(1 1 0) surfaces

The interaction of atomic hydrogen with a cleaved GaAs(1 1 0) surface has been investigated by high resolution electron energy loss spectroscopy. This technique, which is extremely surface sensitive, enables the detection of very small amounts of adsorbate and the indication of the adsorption sites. We have exposed a GaAs(1 1 0) surface to atomic hydrogen in the 10-10⁴ L range. This upper limit corresponds to the onset of the monolayer coverage. The effect of the H exposure is detected in the region of phonon-plasmon losses already at an exposure of 10 L, indicating the occurrence of a band bending. The three layer model for the dielectric function of the GaAs(1 1 0) surface had to be adopted to account for the results. At higher loss energies the stretching vibrations of Ga-H and As-H are also detected from the lowest exposures. The possibility that the As-H signal is given by a double loss (Ga-H + phonon) is ruled out for this surface, therefore, it comes out that from the first stage of interaction H bonds to both Ga and As. The intensity of both Ga-H and As-H signal increases faster than the expected number of adsorbed H atoms suggesting that the dynamical dipole drops drastically with increasing exposure.     

一种可能的InP(100)(4×2)表面原子结构模型

对于用氩离子刻蚀并在磷气氛中退火得到的InP(100)(4×2)再构表面,用HREELS测得表面的In—H和P—H键几乎是同时形成的,而用偏振光UPS观察时,P的悬挂键电子态并不具有沿原胞两个周期方向的对称性质。根据这些结果,可以推测InP(100)的富In表面存在In的空位,与In空位相邻的P原子悬挂键发生了转向。我们提出了一种失列-二聚物原子结构模型。它可以定性地解释所观察到的实验事实。 关键词：     

Hydrogen induced structure changes of GaAs(1 0 0) surfaces

The interaction of hydrogen with GaAs(1 0 0) surfaces has been studied at room temperature by means of high-resolution electron energy-loss spectroscopy (HREELS), low-energy electron-diffraction (LEED), and Auger electron spectroscopy (AES). Sample cleaning by Ne⁺ ion bombardment (500 eV) and annealing resulted (with increasing temperatures) in “1 × 1”, 1 × 6, 4 × 1, 4 × 6 and c(8 × 2) LEED structures. As a function of hydrogen exposure, the intensity ratio of the stretching vibrations (As-H/Ga-H) is shown to be characteristic for the specific reconstructed surface. In particular the arsenic hydride concentration gradually decreased in all cases. In addition, an initial weakening of the fractional order LEED spots occurred with increasing hydrogen exposures. Finally, a strong 1 × 2 structure was observed independent of the reconstruction we started with. Simultaneously, a shift of the energetic position of the Ga-H stretching vibration occurred.     

HREELS of H/GaN(0001): evidence for Ga termination

Two issues relevant to the growth and processing of GaN are the termination of the GaN(0001) surface and its reaction with hydrogen. We have used high-resolution electron energy loss spectroscopy (HREELS), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES) to study the adsorption of hydrogen on MOCVD-grown GaN(0001). LEED of the sputtered and annealed surface shows evidence of facetting. No adsorbate vibrations are observed on the clean surface by HREELS, only Fuchs–Kliewer phonons at intervals of 700 cm⁻¹. Following exposure of the clean GaN surface to hydrogen atoms, HREEL spectra show adsorbate loss peaks at 2580, 3280, and 3980 cm⁻¹. The Ga–H stretching vibration at 1880 cm⁻¹ becomes evident when the HREEL spectrum is deconvoluted to remove the phonon multiple-loss peaks. We assign the 2580, 3280, and 3980 cm⁻¹ peaks to combination modes of the Ga–H stretch and phonon(s). Upon dosing with deuterium, the Ga–D bending mode is observed at 400 cm⁻¹. No vibrational peaks due to N–H (N–D) species are observed after H (D) exposure. We conclude that sputtered and annealed GaN(0001) is Ga-terminated.     

Active sites of adsorption on cleaved and sputtered indium phosphide surfaces

From the initial uptake of atomic hydrogen at room temperature the active sites on cleaved and sputtered InP(110)-surfaces were determined using high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS, XAES). It is found that the In-H stretching mode intensity is dominant for the cleavage surface, which is known to be P-rich due to surface relaxation. For the Ar⁺-ion bombarded surface (In-rich) the P–H stretching mode is very strong if compared to the corresponding In-H mode. From these observations it may be deduced that both, the chemical bonding situation and the geometric configuration, are reflected in our HREELS-results. For the cleavage surface the initial adsorption for atomic hydrogen is interpreted in the framework of existing models for the (1×1) relaxation in terms of its chemical bonding configuration. The sputtered surface is assumed to be amorphous consisting of In-clusters and predominantly broken P-bonds, which are passivated after hydrogen exposure. For high hydrogen exposures, a strong decrease of the phosphor hydride lines may be interpreted as phosphine desorption.     

Si(111)表面吸附氢会形成双氢化相吗?

用热脱附谱研究了原子氢在Si(111)表面的吸附,得到了两个吸附状态。从脱附谱特性同Si(100)/H系统的相似性,可以推测氢在Si(111)表面也存在单氢化相和双氢化相两种状态。单氢化相主要是顶位吸附所形成的,而双氢化相的形成则可以用McRae所提出的Si(111)(7×7)表面原子结构的三角形二聚物层错模型来解释。 关键词：     

Vibrational spectroscopy of oxygen on the (100) and (111) surfaces of lanthanum hexaboride

Reflection absorption infrared spectroscopy (RAIRS) and high resolution electron energy loss spectroscopy (HREELS) have been used to study the adsorption of oxygen on the (100) and (111) surfaces of lanthanum hexaboride. Exposure of the surface at temperatures of 95 K and above to O₂ produces atomic oxygen on the surface and yields vibrational peaks in good agreement with those observed in previous HREELS studies. On the La-terminated (100) surface, RAIRS peaks correspond to vibrations of the boron lattice that gain intensity due to a decrease in screening of surface dipoles that accompanies oxygen adsorption. A sharp peak at ～ 734 cm^?1 in the HREEL spectrum shows isotopic splitting with RAIRS into two components at 717 and 740 cm^?1 with full widths at half maxima of only 12 cm^?1. The sharpness of this mode is consistent with its interpretation as a surface phonon that is well separated from both the bulk phonons and other surface phonons of LaB₆. On the boron-terminated LaB₆(111) surface, broad and weak features are assigned to both vibrations of the boron lattice and of boron oxide. On the (100) surface, oxygen blocks the adsorption sites for CO, and adsorbed CO prevents the dissociative adsorption of O₂.     

Growth and vibrational properties of MnOx thin films on Rh(111)

The growth, structures, and vibrational properties of ultrathin manganese oxide films on Rh(111) had been investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), low energy ion scattering spectroscopy (LEIS) and Auger electron spectroscopy (AES). MnO_x grew in a layer-by-layer fashion on the Rh(111) surface. HREELS phonon features and XPS binding energies showed that an OMnO like tri-layer formed initially. Which was stable on the Rh(111) surface with MnO_x coverage less than one monolayer. At above one monolayer, Mn₃O₄ was preferred as indicated from a four-phonon feature peaked at 13.3, 39, 68 and 83 meV in HREELS. Higher temperature oxidation and annealing were found to improve the long-range order of the MnO_x films.