Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF3 from first‐principles. (6th August 2019)

• Record Type: Journal Article
• Authors: Diao, Yu; Liu, Lei; Xia, Sihao
• Is Part Of: International journal of energy research. Volume 43:Number 13(2019)
• Page Start: 7477
• Page End: 7485
• Publication Date: 2019-08-06
• Subjects: Cs/NF3 -- Cs/O -- first‐principles -- GaAs nanowire photocathode -- negative electron affinity -- surface activation; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.4780
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: We perform a detailed comparative study of Cs/O and Cs/NF3 activation mechanism of negative electron affinity (NEA) GaAs nanowire photocathodes through first‐principles calculations based on density functional theory (DFT). The adsorption energy, Mulliken charge distribution, work function, electron affinity, and dipole moment are analyzed. Results show that the stability of Cs/NF3 co‐adsorption nanowire surface is stronger than that of the Cs/O model. The incorporation of O or NF3 on Cs‐covered nanowire surfaces leads to a sharper decline of surface work function. The NEA states can be attained with both O2 and NF3 . However, during the Cs/O activation process, it needs to strictly control the Cs/O ratio to achieve the maximum photoemission properties of cathode. Moreover, the work function variation of GaAs nanowire photocathodes activated with Cs, O, and NF3 can be explained by the dipole moment model. This work is expected to provide a theoretical guide for improving Cs/O and Cs/NF3 activation procedure for NEA GaAs nanowire photocathodes. Abstract : The first‐principles calculations is employed to investigate the difference of negative electron affinity mechanism for GaAs nanowire photocathodes activated with Cs/O and Cs/NF3 . The systematical stability and some electronic parameters for Cs/O and Cs/NF3 co‐adsorption on GaAs nanowire (10‐10) surfaces are analyzed and compared to maximize the photoemission properties of photocathodes. The simulations are in good accordance with the previous experimental results and expected to direct Cs/O and Cs/NF3 activation procedure of NEA GaAs nanowire photocathodes with higher stability and longer lifetime.