Early stages of Cs adsorption mechanism for GaAs nanowire surface

Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF3from first‐principles

“…The Cs/O and Cs/NF 3 co‐adsorption surface models are established by putting optimized O and NF 3 molecules onto the same Cs‐covered GaAs nanowire (10‐10) surfaces so that the results between these two cases are strictly comparable. Firstly, four single Cs adsorption configurations with different Cs coverage are built to simulate the first‐stage Cs‐only adsorption process . These most stable Cs‐only adsorption configurations are determined on the basis of the minimum principle of adsorption energy, and the corresponding models (eg, 1Cs, 2Cs, 3Cs, and 4Cs adsorption models) are displayed in Figure A.…”

“…12 Based on our previous work, Cs-only and Cs/O co-adsorption on (10-10) surfaces of Zn-doped GaAs nanowires can effectively reduce the material work function, predicting an available method to prepare NEA GaAs nanowire photocathodes. 13,14 Moreover, the NEA state induced by Cs/O activation can be interpreted by various theoretical models, such us the heterojunction, 15,16 the cluster, 17 and double dipole models. 18,19 So far, most research with respect to surface activation of NEA photocathodes has been concentrated on the oxygen-activated surfaces, while little attention is paid to focus on the NEA surfaces treated through Cs and NF 3 .…”

“…The modeling method for GaAs nanowire surfaces can refer to our previous research . Experimental observation has proved that wurzite structure GaAs nanowires are more stable than zinc‐blende structure when the nanowire diameter is below 15 nm.…”

“…13,14 Experimental observation has proved that wurzite structure GaAs nanowires are more stable than zinc-blende structure when the nanowire diameter is below 15 nm. In addition, the natural cleavage planes (10-10) of wurzite structure have lower surface energy compared with (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) planes. 27 Thus, the clean (10-10) surfaces of wurzite GaAs nanowire are established to simulate the surface activation basement.…”

“…The negative electron affinity (NEA) state of GaAs photocathodes is commonly obtained by depositing Cs and oxidant layers (eg, O 2 or NF 3 ) on the ultra‐clean p‐type doping GaAs surfaces, resulting in a low vacuum level below the conduction band minimum (CBM) . Based on our previous work, Cs‐only and Cs/O co‐adsorption on (10‐10) surfaces of Zn‐doped GaAs nanowires can effectively reduce the material work function, predicting an available method to prepare NEA GaAs nanowire photocathodes . Moreover, the NEA state induced by Cs/O activation can be interpreted by various theoretical models, such us the heterojunction, the cluster, and double dipole models .…”