外文翻譯--p型gaas光電陰極銫氧激活層的低能電子顯微鏡和俄歇電子能譜研究（英文）

1、Low energy electron microscopy and Auger electron spectroscopy studies of Cs-Oactivation layer on p-type GaAs photocathodeXiuguang Jin, Alexandre A. C. Cotta, Gong Chen, Alpha T. N`Diaye, Andreas K. Schmid, and Naoto Yam

2、amoto Citation: Journal of Applied Physics 116, 174509 (2014); doi: 10.1063/1.4901201 View online: http://dx.doi.org/10.1063/1.4901201 View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/116/17?ver=p

3、dfcov Published by the AIP Publishing Articles you may be interested in Erratum: “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes” [J. Appl. Phys. 113, 104904 (2013)] J

4、. Appl. Phys. 117, 109901 (2015); 10.1063/1.4914297 Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes J. Appl. Phys. 113, 104904 (2013); 10.1063/1.4794822 The surface acti

5、vation layer of GaAs negative electron affinity photocathode activated by Cs, Li, and NF 3 Appl. Phys. Lett. 95, 174109 (2009); 10.1063/1.3257730 Photoemission study of Cs – N F 3 activated GaAs(100) negative electron a

6、ffinity photocathodes Appl. Phys. Lett. 92, 241107 (2008); 10.1063/1.2945276 Preparation and performance of transmission-mode GaAs photocathodes as sources for cold dc electron beams J. Appl. Phys. 88, 6788 (2000); 10.

7、1063/1.1311307 Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions. Download to IP: 180.85.6.250 On: Thu, 21 Jul 201608:13:04and a steep reflectivity dro

8、p-off observed as start voltage is increased indicates the electron injection threshold. De-convolution procedures permit very accurate measure- ments of work function changes;19 here, we use the intersec- tion of tangen

9、ts fitted to the reflectivity above and below electron injection threshold (see Fig. 1). Our photocathodes were made of chips cut from a com- mercial p-type (001) GaAs bulk wafer with Zn dopant concentration of ?1019cm?3

10、. The GaAs chips were cleaned by Ar ion sputtering at 1.5 kV and annealing at 500 ?C and surface purity was confirmed by AES measurements. For NEA surface preparation, the GaAs chips were transferred into the LEEM chambe

11、rs, where the chips were illuminatedusing a 785 nm semiconductor laser. The GaAs chips were activated by cycles of Cs and O deposition in a “yo-yo” treatment; Cs was deposited until the QE decreased to almost zero and af

12、ter that, O was supplied at a pressure of ?10?7 Pa until the QE reached a maximum. We also performed a reversed “yo-yo” treatment, where O was dosed to quench QE close to zero, followed by Cs depositions to maximize QE.

13、Again, these cycles were repeated until the peak QE showed saturation.III. RESULTSFigure 1 shows the electron reflectivity versus electron beam energy for clean p-type GaAs and p-type GaAs after the yo-yo treatment. In t

14、he work function energy scale, zero point was defined as the vacuum level of the p-type GaAs. We find that the preparation of the NEA surface lowers the work function by about 3.5 eV. Figure 2 shows time dependence of em

15、ission current and work function change during the different NEA prepara- tions. In the conventional yo-yo treatment shown in Fig. 2(a), the QE is increased and decreased, respectively, as a function of repeated O and Cs

16、 depositions. Cycles are reversed in the R-yo-yo treatment shown in Fig. 2(b), where the QE is increased and decreased, respectively, as a function of Cs and O depositions. In both treatments, QE shows higher values afte

17、r each Cs and O cycle. The work function change also shows cyclical increases and decreases, which coincide with the emission current variations. The maximal QE achieved after the yo-yo treatment is higher than that reac

18、hed after the R-yo-yo treatment. An AES spectrum col- lected after the yo-yo treatment is shown in Fig. 3, where the peak size of the Cs 563 eV signal is larger than the oxygen 502 eV signal. Estimating the Cs/O ratios b

19、y multiplying theFIG. 1. Reflectivity versus start voltage for GaAs after cleaning (blue line) and after NEA preparation (red line). Work function change is determined by measuring the intersection of tangents fitted to

20、the reflectivity drop-off above injection threshold (dashed lines).FIG. 2. Emission current and work function change during (a) yo-yo treatment and (b) R-yo-yo treatment. Inset in panel (a) shows a PEEM image of a freshl

21、y prepared cathode, field of view is 14 lm.174509-2 Jin et al. J. Appl. Phys. 116, 174509 (2014)Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions. Downl