In this work, the desorption of diphenylamine from different five types of porous Si substrates under low vacuum (10(-2) Ton) is examined. These substrates include (i) freshly prepared porous Si; (ii) ambient-oxidized porous Si, and rapidly oxidized porous Si samples processed at the maximum temperatures of (iii) 400 degrees C, (iv) 600 degrees C, and (v) 1180 degrees C. A typical experiment involves the measurement of the rate of desorption as a function of surface morphology, composition, and temperature. These results suggest that desorption from the porous matrix is limited by strong capillary forces and can be overcome by external factors such as temperature. The chemical composition of the porous Si surface also plays a role in desorption and can increase or lower desorption rates. The dearest difference in diphenylamine desorption behavior is detected between the freshly prepared porous Si surface and porous Si samples rapid thermally oxidized at 600 and 1180 degrees C.