Spectroscopic evidence for the formation of 3-D crystallites during isothermal heating of amorphous ice on Pt(1 1 1)

The formation of crystalline ice through isothermal heating of 80 layers amorphous ice on Pt(1 1 1) at 150 K is studied using X-ray photoelectron spectroscopy and infrared reflection absorption spectroscopy. An early indicator for inhomogeneous crystallization is provided by the uncharacteristically high Pt 4f photoelectron peak for crystalline ice compared with the corresponding uniformly thick amorphous case. O 1s photoelectron spectra unambiguously show that the first monolayer is exposed after crystallization at multilayer total coverage. Using the relative intensities between the first monolayer and multilayer contributions to the O 1s photoelectron spectra, we estimated that ∼46% and ∼80% of the first monolayer is exposed to vacuum with an average crystallite height of ∼41 and ∼31 layers for an equivalent total coverage of ∼23 and ∼7 layers, respectively.