The electron-stimulated desorption of metastable molecular nitrogen (N-2*) from N-2 condensed onto n-hexane spacer films deposited on Pt(111) is investigated as a function of electron-impact energy (5-25 eV), and thickness (1-20 monolayers) and deposition temperature (T=20-80 K) of the n-hexane layer. At low T, the N-2* yield is found to be inversely proportional to the thickness of the amorphous n-hexane layer. This behavior is explained by the existence of a porous structure in the n-hexane film which efficiently absorbs N-2. The metastable signal is also strongly dependent on the temperature of n-hexane deposition, which controls the morphology of the spacer from amorphous at low T to crystalline at T>70 K. Increasing the deposition temperature of n-hexane from 20 to 70 K results in an increase of the N-2* signal due to the decrease of the pore volume. Formation of the n-hexane layers in the crystalline state at higher temperatures further inhibits N-2 migration into the spacer which results in further increases in the magnitude of the N-2* desorption signal.