Analysis of Laser-Enhanced Adsorption/Desorption Processes on Semiconductor Surfaces via Electronic Surface State Excitation

1982 ◽  
Vol 17 ◽  
Author(s):  
William C. Murphy ◽  
A. C. Beri ◽  
Thomas F. George ◽  
Jui-Teng Lin
Keyword(s):  
Laser Radiation ◽  
Energy Gap ◽  
Surface States ◽  
Surface Region ◽  
Direct Excitation ◽  
Enhanced Adsorption ◽  
A Charge ◽  
Selective Enhancement ◽  
Adsorption Desorption ◽  
Electronic Surface

ABSTRACTElectronic surface states in semiconductors often lie between the valence and conduction bands and give rise to charge densities confined to the surface region. Laser radiation of frequency less than the energy gap can excite electrons from delocalized valence band states to these localized surface states leading to large changes in the charge distribution at the surface. Selective enhancement of adsorption/desorption processes involving ionic or polar adspecies can result from such a charge redistribution. Using a onedimensional model for silicon, the cross-section for the laser-induced electronic transition to surface states is shown to be large. The interaction energy of an adspecies with the surface changes significantly with direct excitation of surface states in a semiconductor. For a one-dimensional metal, however, direct transitions between bulk and surface states are not allowed, but phonon-mediated transitions coupled with laser radiation lead to substantial charge transfer as for semiconductors.

Electronic surface states in GaAs/Ga1 − xAlxAs superlattice: effect of surface location

Vacuum ◽  
1995 ◽  
Vol 46 (5-6) ◽  
pp. 459-463 ◽  
Author(s):  
M Stȩślicka ◽  
R Kucharczyk ◽  
EH El Boudouti ◽  
B Djafari-Rouhani ◽  
ML Bah ◽  
...  
Keyword(s):  
Surface States ◽  
Surface Location ◽  
Electronic Surface ◽  
Effect Of Surface

scholarly journals Covalent assembly of a two-dimensional molecular “sponge” on a Cu(111) surface: confined electronic surface states in open and closed pores

2014 ◽  
Vol 50 (57) ◽  
pp. 7628-7631 ◽  
Author(s):  
Aneliia Shchyrba ◽  
Susanne C. Martens ◽  
Christian Wäckerlin ◽  
Manfred Matena ◽  
Toni Ivas ◽  
...  
Keyword(s):  
Surface States ◽  
Two Dimensional ◽  
New Class ◽  
Trimesic Acid ◽  
Electronic Surface

We present a new class of on-surface covalent reactions, formed between diborylene-3,4,9,10-tetraaminoperylene and trimesic acid on Cu(111), which gives rise to a porous 2D-‘sponge’.

scholarly journals Study on synthesis of MoS2 modified g-C3N4 materials for treatment of Direct black 38 dye

2018 ◽  
Vol 9 (3) ◽  
pp. 169-176
Author(s):  
Thi Lan Phung ◽  
Thi Kim Giang Nguyen
Keyword(s):  
Visible Light ◽  
Visible Light Irradiation ◽  
Photocatalytic Performance ◽  
Ph Value ◽  
Light Irradiation ◽  
Order Kinetic ◽  
Two Factors ◽  
Pseudo Second Order ◽  
Enhanced Adsorption ◽  
Adsorption Desorption

Pure g-C3N4 and MoS2 modified g-C3N4 materials were synthesized using a facile heating method and a low-temperature hydrothermal method, respectively. The obtained samples were characterized by XRD pattern and N2 adsorption-desorption technique at 77K. The adsorption and photocatalytic performance of all obtained samples were investigated by discoloration of direct black 38 dye in the dark and under visible light irradiation. The results showed that all obtained samples exhibited good discoloration efficiency of direct black 38 dye. The two factors including pH values and Mo loading effected mainly on elimination efficiency of direct black 38 dye. MoS2 modified g-C3N4 materials possessed the more enhanced adsorption and photocatalytic performance in comparison to pure g-C3N4 at pH value of 3.5, with adsorbent dosage of 0.1 g/L. Furthermore, it was found that the adsorption process and photo-catalysis simultaneously occurred under visible light irradiation and followed up a pseudo-second-order kinetic reaction of Langmuir - Hinshelwood model. g-C3N4 và g-C3N4 biến tính bởi MoS2 đã được tổng hợp theo phương pháp nung đơn giản và phương pháp thủy nhiệt ở nhiệt độ thấp tương ứng. Các mẫu tổng hợp đã được đánh giá đặc trưng bởi các phương pháp hiện đại như giản đồ nhiễu xạ tia X, phương pháp hấp phụ-khử hấp phụ N2 ở 77K. Khả năng hấp phụ và quang hóa xúc tác của các vật liệu tổng hợp đã được nghiên cứu bởi quá trình phân hủy màu thuốc nhuộm direct black 38 trong điều kiện bóng tối và chiếu sáng bởi ảnh sáng nhìn thấy của đèn chiếu sáng sợi đốt wolfram (220V-100W). Các kết quả nghiên cứu chỉ ra rằng các mẫu tổng hợp đều có hiệu suất xử lý màu cao đối với thuốc nhuộm direct black 38. Hai yếu tố gồm pH dung dịch và hàm lượng MoS2 ảnh hưởng chính đến hiệu suất xử lý màu direct black 38. g-C3N4 biến tính bởi MoS2 luôn thể hiện hiệu suất hấp phụ và quang hóa cao hơn so với g-C3N4 tinh khiết. Hơn nữa, khi được chiếu sáng bởi ánh sáng nhìn thấy thì quá trình hấp phụ và quá trình quang hóa thuốc nhuộm direct black 38 trên các vật liệu tổng hợp đã xảy ra đồng thời và mô hình Langmuir - Hinshelwood động học bậc 2 đã được đề xuất cho quá trình này.

Direct excitation of potassium diffuse bands by single mode laser radiation

1986 ◽  
Vol 2 (3) ◽  
pp. 233-238 ◽  
Author(s):  
?. Vadla ◽  
K. Niemax ◽  
G. Pichler
Keyword(s):  
Laser Radiation ◽  
Single Mode ◽  
Mode Laser ◽  
Single Mode Laser ◽  
Direct Excitation

scholarly journals Robust edge photocurrent response on layered type II Weyl semimetal WTe2

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Qinsheng Wang ◽  
Jingchuan Zheng ◽  
Yuan He ◽  
Jin Cao ◽  
Xin Liu ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Surface States ◽  
Separation Mechanism ◽  
Current Response ◽  
Type Ii ◽  
Nonlinear Optical Effect ◽  
Linear Dispersion ◽  
Weyl Semimetal ◽  
Quantum Materials ◽  
A Charge

AbstractPhotosensing and energy harvesting based on exotic properties of quantum materials and new operation principles have great potential to break the fundamental performance limit of conventional photodetectors and solar cells. Weyl semimetals have demonstrated novel optoelectronic properties that promise potential applications in photodetection and energy harvesting arising from their gapless linear dispersion and Berry field enhanced nonlinear optical effect at the vicinity of Weyl nodes. In this work, we demonstrate robust photocurrent generation at the edge of Td-WTe2, a type-II Weyl semimetal, due to crystalline-symmetry breaking along certain crystal fracture directions and possibly enhanced by robust fermi-arc type surface states. This edge response is highly generic and arises universally in a wide class of quantum materials with similar crystal symmetries. The robust and generic edge current response provides a charge separation mechanism for photosensing and energy harvesting over broad wavelength range.

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