AVS2001 Session SS2-TuP: Semiconductor Reactions Poster Session
Tuesday, October 30, 2001 5:30 PM in Room 134/135
Tuesday Afternoon
Time Period TuP Sessions | Topic SS Sessions | Time Periods | Topics | AVS2001 Schedule
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SS2-TuP-1 XPS Investigation of Trimethylsilane Dosed Ge (100) Surfaces
P.W. Wang (The University of Texas at El Paso); Y. Qi (University of Massachusetts); J.H. Craig (Bradley University) Trimethylsilane (TMSi) was dosed onto a sputter cleaned Ge (100) surface at 145 + 5 oC and X-ray photonelectron spectroscopy (XPS) was used to study the cumulative effect of dosage, electron irradiation, temperature, and X-ray photon irradiation. The core level C 1s, Si 2p and Ge 3d photoelectrons were monitored. Arguments based on electronegativities of C, Si, and Ge and bond strengths of C-C, C-Si and C-Ge are invoked to interpret the interaction of TMSi with the Ge (100) surface under various external conditions. It is demonstrated that TMSi dissociatively chemisorbs initially at low coverage, but physisorbs molecularly at high coverage. Both electron irradiation and thermal effects cause the breaking of C-C or C-H bonds. New bonds of C-Ge are formed as a consequence. X-ray photon induced secondary electrons and local heating result in the dissociation of the adsorbed C-H or Si-H species which causes the initial concentration increase of Ge-C bonds. This study clearly shows the different pathways to form new species on the Ge (100) surfaces under various external conditions. |
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SS2-TuP-3 Generation of Type-C Defects on Si(100) by Bimolecular Adsorption of Water: A FT-IR, STM, AES and QMS Study
M. Nishizawa, T. Yasuda, S. Yamasaki (Joint Research Center for Atom Technology (JRCAT), Japan); K. Miki (National Institute of Advanced Industrial Science and Technology (AIST), Japan); M. Shinohara, N. Kamakura, Y. Kimura, M. Niwano (Tohoku University, Japan) STM studies on various processes on Si(100)-(2x1) are often interfered with a high density of surface defects. Among three types of defects reported on this surface,1 the structure of the so-called type-C defect has been under debate. We show that the C-defects are generated by adsorption of water from the UHV environment. This conclusion is based on our systematic investigations using FT-IR, STM, AES, and QMS. Our STM experiments have reproduced the commonly observed phenomenon that the C-defect density increases with time even when the vacuum is as good as 10-11 Torr. The surface with many C-defects shows a small but detectable OKLL signal in AES. A possible source of O is the residual H2O, CO, and/or CO2 in UHV. To identify the source of surface O, we examined the correlation between the generation rate of the C-defects and the partial pressures for these gases. We have found that H2O, which adsorbs at a sticking probability near unity, is the only candidate that can account for the defect generation rate. Dissociative adsorption of residual H2O has been indeed detected by our IR measurements in which Si-H and O-H stretching modes are observed. The Si-H band has two components indicating that there are two kinds of Si-H bonds of different configurations. In addition, kinetic analyses of the Si-H evolution have revealed that the adsorption takes place via highly mobile precursor states. These observations suggest that C-defects are generated by bimolecular adsorption of H2O, which readily explains the STM observation that the C-defects occupy two dimers. The detailed structure of the C-defect will be discussed at the presentation. This study, partly supported by NEDO, was performed at JRCAT under the joint research agreement between AIST and ATP. |
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SS2-TuP-5 Investigation of Surface Intermediates in Thermal Decomposition of Diethylmethylsilane on Si(111) using Low Energy Cs Ion Scattering and Thermal Desorption Spectroscopy
H.-G. Chi, Y. Kim, J.-H. Boo, S.K. Kim, S.-B. Lee (Sungkyunkwan University, Korea); H.T. Kwak (Kook Min University, Korea) The intermediate species produced in the decomposition of diethylmethylsilane on Si(111) were investigated in the range of 110 1200 K by using Cs+ reactive ion scattering (RIS), low energy secondary ion mass spectrometry (SIMS) and thermal desorption spectroscopy. We will show that RIS gives more reliable evidence than SIMS for identification of surface species of this system. The results of low energy Cs+ ion scattering indicate that molecular diethylmethylsilane and various alkylsilyl species such as (C2H5)2Si, C2H5SiCH3, C2H5Si, and CH4Si as well as hydrocarbon species such as C2H4 and C2H5 exist on surface between 110-150 K. Above 300 K, all the alkylsilyl species are converted to CH4Si, which decomposes completely to form SiC above 900 K. We will propose a possible mechanism for the SiC formation from the results of low energy ion scattering and thermal desorption spectroscopy. |
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SS2-TuP-6 Interface Reaction of Cesium Layers Deposited on a H-terminated CVD Diamond
S. Yoshida, T. Inaba, T. Urano, S. Hongo (Kobe University, Japan) CVD diamond is potential for negative electron affinity (NEA)materials. Therefore, H-terminated and alkali adsorbed diamond surfaces have been studied intensively. It has been known that getting clean diamond surface is difficult. Because Ar ion sputtering and electron irradiation may result in amorphization of the diamond structure and heating the amorphous layer results in the formation of graphitic clusters. Cyclic adsorption and desorption of hydrogen also degrades the surface. Like this, the diamond surface is complicated and has inherent instability compared with Si surface. Therefore it is neccessary to reveal interface reaction to produce stable NEA devices. In this study hot-filament CVD diamond was used. All experiments were carried out in a UHV chamber equipped with thermal desorption spectroscopy, metastable deexcitaion spectroscopy, ultra violet photoelectron spectroscopy and Auger electron spectroscopy (AES). Cesium was deposited using SAES gettters Cs dispenser at 150 K. Atomic hydrogen produced by hot filament was used to terminate the diamond surface. It was found that 1)Multilayer(island) Cs is formed on Ar ion sputtered surface, 2)Multilayer(island) Cs desorption peak is not observed on a H-terminated surface, 3)Clear H2 desorption peak attributed to Cs-H bond foirmation (which is seen for Cs/H-terminated Si(100) sample) is not observed for Cs/H-terminated CVD diamond, 4)As raising the sample(Cs/H-terminated CVD diamond) temperature from 150 K to 470 K, AES peak of Cs decreases and that of C increases, though no Cs and H2 desorption peak are observed during heating. These experiments may suggest the formation of Cs-C-H mixture at low temperatures. |