Effect of Ferroelectric Poling on the Adsorption of 2-Propanol on LiNbO₃(0001)

Abstract

The effect of ferroelectric poling on the surface chemistry of ferroelectric materials was studied through the adsorption and temperature-programmed desorption (TPD) of 2-propanol on the positively and negatively poled LiNbO 3 (0001) surfaces. Although only molecular adsorption and desorption were observed on both surfaces, the desorption peak temperature of 2-propanol from the positive surface was over 100 K higher than that from the negative surface, indicating that the polar molecule adsorbs more strongly on the positive surface. Furthermore, the 2-propanol desorption peak temperature depended unusually strongly on the heating rate, yielding apparent desorption pre-exponentials on the order of 10 s -1 for the positive surface and 10 -1 s -1 for the negative surface. These unusually low numbers could be associated with the pyroelectric behavior of LiNbO 3 creating a temperature-dependent surface dipole; interaction of the polar molecule with this surface dipole then causes the desorption activation energy to also depend on temperature. Fitting the data to a simple linear model between the desorption activation energy and temperature suggests that the desorption activation energy of 2-propanol from LiNbO 3 increases by about 0.25 kJ/mol-K as the temperature increases. Taking this effect into account, the data indicate an 11 kJ/mol higher desorption activation energy from the positive surface. The results also revealed a sensitivity of the adsorption/desorption to the morphology of the opposite face of the crystal.

Ferroelectric polarization dependent interactions at Pd–LiNbO3(0001) interfaces

“…21,22 Following the convention used in previous studies, the positive ͑c + ͒ face corresponds to one that had a negative pyroelectric voltage, and the negative ͑c − ͒ face to the one that had a positive voltage. 9,21 Experiments were performed using an ultrahigh vacuum chamber ͑base pressure, 2 ϫ 10 −10 torr͒ equipped with a mass spectrometer ͑UTI 100C͒, which was used for TPD experiments, and a cylindrical electron energy analyzer ͑Omicron͒ and an electron gun, which were used to collect AES data. The electron beam diameter during the collection of AES spectra was ϳ1 mm.…”

“…4 It has also been suggested that the ability to manipulate the orientation of the ferroelectric dipole property could be used to tune surface reactivity. [5][6][7][8][9][10][11][12][13][14][15][16] Several examples indicating that this may indeed be the case have recently appeared in the literature. 5,6,8,9,[14][15][16][17][18] For example, the rate of photoreduction of aqueous Ag+ ions 5,6 on BaTiO 3 and PZT ͑Ref.…”

“…18͒ surfaces, and the sticking coefficients and interaction energies of alcohols and water with BaTiO 3 ͑Refs. 14-16͒ and LiNbO 3 surfaces 8,9,12,13 have all been shown to be dependent on the polarization direction.…”

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯Zhu1, Morales-Acosta2, Shen3 et al. 2015Phys. Rev. BSelf Cite10030View full textAdd to dashboardCite

“…For example, the common ferroelectric materials LiNbO 3 and PbTiO 3 display polarization direction-dependent adsorption of polar molecules but the thermodynamically favored surfaces of both materials are catalytically inert. [20][21][22][23] Theoretical studies have suggested that ultrathin transition metal layers on ferroelectric surfaces can display unique catalytic properties. For example, it has been suggested that CO can dissociate on Pt on negatively poled PbTiO 3 , 24 chemistry that is not observed on any known form of Pt.…”

Defect-mediated adsorption of methanol and carbon dioxide on BaTiO3(001)

“…9,10 Recently, it has also been found that the adsorption and desorption energetics of various molecules ͑e.g., alcohols, acetic acid, carbon dioxide, and water͒ on ferroelectric substrates ͓e.g., LiNbO 3 , BaTiO 3 , and Pb͑Zr 0.52 Ti 0.48 ͒O 3 or PZT͔ are affected by the substrate polarization. [11][12][13][14][15][16][17][18] Predicting the effect of polarization reversal on moleculesurface interactions is challenging because there are several factors to consider, including electrostatic effects due to surface polarization charge and screening charge 19 as well as possible differences in the stoichiometry and arrangement of atoms at oppositely poled surfaces. 20,21 However, molecular adsorption on surfaces is often site specific, so one way to address this challenge is to identify the adsorption sites for molecules on a given surface and then to examine how polarization reversal affects the electronic and geometric structure of these sites, for example, through the use of scanning probe microscopy techniques.…”