PREPARATION OF METALLIC THIN FILM PHOTOCATHODES BY PULSED LASER DEPOSITION F. Gontad National Institute of Nuclear Physics Department of Mathematics and Physics “Ennio de Giorgi” University of Salento, Lecce, Italy

OUTLINE

¢  PLD

technique ¢  Superconducting photocathodes —  — 

Deposition and Characterization Testing

¢  New — 

configuration photocathodes

Deposition and Characterization

¢  Summary

BASIC PRINCIPLES OF PULSED LASER DEPOSITION (PLD)

Ø  FILMS NOTABLY ADHERENT TO THE SUBSTRATE; Ø  HIGH QUALITY FILMS; Ø  VERSATILE TECHNIQUE.

PLD SET-UP Target-­‐substrate   distance  

50  mm  

Laser  spot  size  

1.2  mm  

Vacuum  level  

3×10-­‐6  Pa  

Q-switch frequencyquadrupled Nd:YAG laser (λ = 266 nm, τ = 7 ns) Dye KrF Excimer laser (λ = 248 nm, τ = 0.5, 5 ps)

METALIC PHOTOCATHODES PREPARED BY PLD Material  

λ   (nm)  

Pulse     length  

REFERENCES  

Mg  

308    

30  ns  

L.  Cultrera  et  al.,  Appl.  Surf.  Sci.  (2005)   L.  Cultrera  et  al.,  J  of  Phys.  D  (2007)  

Y  

308   266  

30  ns   7  ns  

L.  Cultrera  et  al.,  J  Nanosci.  Nanotech.  (2009)   F.  Gontad  et  al.,  Thin  Solid  Films  (2012)  

266   1064   248  

  7  ns   5  ps   0.5  ps  

F.  Gontad  et  al.,  Thin  Solid  Films  (2012)   A.  Perrone  et  al.,  NIMA  (2013)   F.  Gontad  et  al.,  Phys.  Rev.  ST-­‐accel  (2013)   F.  Gontad  et  al  ,  NIMA  (2014)    

7ns   5  ps  

A.  Lorusso  et  al.,  NIMA  (2013)   F.  Gontad  et  al.  (to  be  published)  

Pb  

 

 

   

Cu  

266   248  

OUTLINE ¢  Common

photocathode materials ¢  PLD technique ¢  Superconducting photocathodes —  — 

Deposition and Characterization Testing

¢  New — 

configuration photocathodes

Deposition and Characterization

¢  Further

work

LEAD PHOTOCATHODES

248 nm 0.5 ps

248 nm 5 ps

266 nm 7 ns

PHOTODIODE CELL

LEAD PHOTOCATHODES QE

Laser cleaning induces smoothing of cathode surface Q-switch frequencyquadrupled Nd:YAG laser (λ = 266 nm, τ = 7 ns)

LEAD PHOTOCATHODES QE

THIN FILM LEAD PHOTOCATHODES ¢  Good

adherence

¢  Reasonably ¢  Stable

good QE

under vacuum conditions

OUTLINE ¢  PLD

technique ¢  Superconducting photocathodes —  — 

Deposition and Characterization Testing

¢  New — 

configuration photocathodes

Deposition and Characterization

¢  Further

work

NEW APPROACH

266 nm 7 ns

NEW APPROACH

FILM MORPHOLOGY

(

)

! = 2.3 ± 0.1 !10"6 #cm

SUMMARY ¢ 

¢ 

¢ 

¢ 

THIN COPPER FILMS CAN BE DEPOSITED; COPPER FILMS PRESENT A GOOD ADHERENCE TO THE YTTRIUM SUBSTRATE; SURFACE RESISTIVITY IS SIMILAR TO BULK RESISTIVITY; UNIFORM FILMS WITH A LOW CONTAMINATION LEVEL CAN BE DEPOSITED.