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

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.