In devices based on CdS, indium is often used to make Ohmic contacts. Since indium is scarce and expensive, suitable replacement materials need to be found. In this work, we show that sputtered titanium nitride forms an Ohmic contact with n-type CdS. The CdS films, deposited with chemical bath deposition, have a hexagonal crystal structure and are polycrystalline, mostly with a (002) texture. The thickness of the films is $600 nm, and the donor density is 1.9 Â 10 16 cm À3. The donor density increases to 1.5 Â 10 17 cm À3 upon annealing. The contact resistivity of sputtered TiN on CdS is found to be 4.7 6 0.6 X cm 2 . This value is sufficiently small to avoid large resistive losses in most CdS device applications. To demonstrate the use of TiN in a CdS device, a Au/CdS/ TiN Schottky diode was constructed. The diode has a potential barrier of 0.69 V and an ideality factor of 2.2.

The design of a fluidized bed atomic layer deposition (ALD) reactor is described in detail. The reactor consists of three parts that have all been placed in one protective cabinet: precursor dosing, reactor, and residual gas treatment section. In the precursor dosing section, the chemicals needed for the ALD reaction are injected into the carrier gas using different methods for different precursors. The reactor section is designed in such a way that a homogeneous fluidized bed can be obtained with a constant, actively controlled, reactor pressure. Furthermore, no filters are required inside the reactor chamber, minimizing the risk of pressure increase due to fouling. The residual gas treatment section consists of a decomposition furnace to remove residual precursor and a particle filter and is installed to protect the pump. In order to demonstrate the performance of the reactor, SiO2 particles have been coated with TiO2 using tetrakis-dimethylamino titanium (TDMAT) and H2O as precursors. Experiments with varying pulse times show that saturated growth can be obtained with TDMAT pulse times larger than 600 s. Analysis of the powder with High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) and energy dispersive X-ray spectroscopy confirmed that after 50 cycles, all SiO2 particles were coated with a 1.6 nm homogenous shell of TiO2.

Atomic layer deposition was used to coat CdS photoanodes with 7 nm thick TiO2films to protect them from photocorrosion during photoelectrochemical water splitting. Photoelectrochemical measurements indicate that the TiO2coating does not provide full protection against photocorrosion. The degradation of the film initiates from small pinholes and shows oscillatory behavior that can be explained by an Avrami-type model for photocorrosion that is halfway between 2D and 3D etching. XPS analysis of corroded films indicates that a thin layer of CdS remains present on the surface of the corroded photoanode that is more resilient towards photocorrosion.

Conductive TiN shells have been deposited on SiO 2 nanoparticles (10-20 nm primary particle size) with fluidized bed atomic layer deposition using TDMAT and NH 3 as precursors. Analysis of the powders confirms that shell growth saturates at approximately 0.4 nm/cycle at TDMAT doses of [1.2 mmol/g of powder. TEM and XPS analysis showed that all particles were coated with homogeneous shells containing titanium. Due to the large specific surface area of the nanoparticles, the TiN shells rapidly oxidize upon exposure to air. Electrical measurements show that the partially oxidized shells are conducting, with apparent resistivity of approximately *11 kX cm. The resistivity of the powders is strongly influenced by the NH 3 dose, with a smaller dose giving an order-of-magnitude higher resistivity.

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