Ultra-high vacuum surface science techniques use electrons or ions as probes that interact with matter sufficiently strongly that surface-specific information is obtained. Typically, a combination of techniques is used to characterise a surface as completely as possible. Table 12.1 List of vacuum techniques used to characterise semiconductor surfaces. Technique Particle/photons in/out Information depth/nm Type of […]

For fuel-generating photoelectrochemical devices, it is desirable to determine chemical products dynamically in situ during potential variations. This is possible when mass spectroscopy is coupled to electrochemical experiments via specific membranes that are permeable to volatile chemicals but which separate the electrolyte from a vacuum chamber linked to the mass spectrometer (Bittins-Cattaneo et al 1991; […]

Photoelectrochemical mechanisms may be characterised by potential-dependent structural changes of the photoactive interfaces. These may include stoichiometric changes (e. g. intercalation or excalation of ionic species), phase changes or dynamic molecular changes of photocatalytic species. In all these cases, time-dependent structural information is desirable. This may be accomplished with in-situ X-ray and EXAFS (X-ray absorption […]

If, instead of measuring integral parameters of an energy-converting interface, a spatially resolved image is produced of a relevant quantity such as photocurrent, photopotential or microwave conductivity, luminescence or electroreflectance, significantly more information is available. Such a spatially-resolved image of a semi­conductor interface typically shows patterns determined by inhomogeneities of the material or surface preparation. […]

The interpretation of IMPS data relies on the competition between charge transfer and recombination to give a semicircle that can be analysed to obtain kct and krec. It follows that IMPS provides no information if recombination is absent. Surface recombination usually becomes negligible at potentials sufficiently far from the flatband potential, where a plateau is […]

The basic measurement technique for intensity-modulated photovoltage spectroscopy (IMVS) is the same as for IMPS. In principle, IMVS measurements can be made for any constant current condition, but in practice it is usual to make measurements under conditions where the net current is zero. In the case of a photoelectrochemical solar cell, this corresponds to […]

In photocalorimetry, the relative temperature change of a photoactive electrode is measured as a function of the electrode potential under chopped monochromatic illumination (Fujishima et al., 1977; Rappich and Dohrmann, 1989; Dohrmann and Schaaf, 1992; Dohrmann and Reck, 1998). Either pyroelectric or piezoelectric sensors or photoacoustic microphones are coupled to the back surface of the […]

12.6.1 Electrolyte electroreflectance spectroscopy Electrolyte electroreflectance (EER) spectroscopy of semiconductors is based on the use of a transparent electrolyte contact to form a Schottky barrier in which the electric field perturbs the optical constants (i. e. the real and imaginary components of the complex dielectric function) of the solid. Under depletion conditions, the width of […]