Effect of humid air exposure on photoemissive and structural properties of KBr thin film photocathode

TL;DR

This study examines how humid air exposure at 65% RH affects the photoemissive efficiency and surface structure of KBr thin film photocathodes, revealing exponential yield degradation and morphological changes without altering crystalline structure.

Contribution

It provides new insights into the effects of humidity on KBr photocathodes, combining photoemission, structural, and topographical analyses to understand degradation mechanisms.

Findings

Photoelectron yield decreases exponentially with humid air exposure.

Crystalline structure remains unchanged despite humidity exposure.

Surface morphology shows significant granular alterations after short-term humid air contact.

Abstract

We have investigated the influence of water molecule absorption on photoemissive and structural properties of potassium bromide (KBr) thin film photocathode under humid air exposure at relative humidity (RH) 65%. It is evident from photoemission measurement that the photoelectron yield of KBr photocathode is degraded exponentially with humid air exposed time. Structural studies of the "as-deposited" and "humid air aged" films reveal that there is no effect of RH on film's crystalline face centered cubic (fcc) structure. However, the average crystallite size of "humid air exposed film" KBr film has been increased as compared to "as-deposited". In addition, topographical properties of KBr film are also examined by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) and it is observed that granular characteristic of film has been altered, even for short exposure to humid air.