Mo(110)面上的碳化結構與其活性探討

Investigation of carbide structures and their reactivity on Mo(110) surface

林榮彬(Rong-Bin Lin)

指導教授 ： 羅榮立

國立清華大學/理學院/物理學系/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00156

摘要

摘要

過渡金屬碳化物具有特別的物理和化學性質。就物理性質來講，過渡金屬碳化物同時具有共價性固體、離子性晶體、過渡金屬的優點。且廣泛應用在去氫、氫化、氫解等各方面。而鉑族金屬也具有這類功用。但鉑族金屬價格昂貴，過渡金屬碳化物的性能也不比鉑族金屬差，故過渡金屬碳化物成為多人研究的方向。
過渡金屬碳化物分為四類：bulk carbides、carbide-modified surfaces、carbide thin films、carbide clusters。本實驗所進行鉬（110）面碳化為carbide-modified surfaces。carbide-modified surfaces的晶格結構不如碳化物單晶般完美，但好處是可以自由控制碳原子比例，且可以保有高導電率、高熱導率、高硬度、高熔點的特性。根據以往相關文獻對其碳化結構的研究大都侷限於LEED和AES的觀察，而碳化表面的實際結構還不是很清楚。
本實驗分成兩個主軸：其一為對乾淨的鉬(110)面作碳化。控制的條件包括乙烯的曝量、曝氣時的溫度、離子槍的能量、退火的溫度、退火的時間長短等。接著對碳化後的表面作LEED及STM的量測，歸納出表面碳化結構和控制變數間的關聯。其二是對碳化後的表面曝氧氣，並作STM的量測，比較碳化後的表面曝氧前後的差異。

關鍵字

鉬(110)面 ； 碳化 ； 碳化後曝氧

並列摘要

Abstract

TMC have special physical and chemical properties. They have the properties of covalent solids, ionic crystals, and transition metals at the same time. They are applied in a variety of processes, such as dehydrogenation, hydrogenation, and hydrogenolysis. Due to their comparable performance, TMCs are the potential substitutes for the expensive Pt-group metals in catalysis applications. Therefore, they attract intense interests in both fundamental researches and industrial applications.
Transition metal carbides are divided into four groups: bulk carbides, carbide-modified surfaces, carbide thin films, carbide clusters. Our carbonization experiment is focusd on carbide-modified surfaces of Mo(110). Although the crystal structure of carbide-modified surfaces is not as good as bulk single crystal carbides, its qualities, such as electric conductivity, thermal conductivity, hardness, and melting temperature, can be controlled via the carbon/metal stoichiometry. In the literature, the researches of carbide surface structures mostly confine to observation of LEED and AES, the real structure of carbide surfaces is still not clear.
This experiment is divided into two parts. Firstly, carbide overlayers were fabricated on clean Mo(110) surfaces. The tunable parameters include exposures, temperature during carbonization, annealing temperature, annealing time. The relations between carbide surface structures and varing parameters were investigated by LEED and STM. Secondly, oxygen exposure on carbide surfaces, the reactivity of carbide structures on oxygen was compared before and after exposure of oxygen by STM.

參考文獻

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參考文獻

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