The electrical transport in amorphous titanium dioxide (a-TiO 2 ) thin films deposited by atomic-layer deposition (ALD), and across heterojunctions of p + -Si|a-TiO 2 |metal substrates that had various top metal contacts, has been characterized by AC conductivity, temperaturedependent DC conductivity, space-charge-limited current (SCLC) spectroscopy, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and current density versus voltage (J-V) characteristics. Amorphous TiO 2 films were fabricated using either tetrakis(dimethylamido)-titanium (TDMAT) with a substrate temperature of 150 °C or TiCl 4 with a substrate temperature of 50, 100, or 150 °C. EPR spectroscopy of the films showed that the Ti 3+ concentration varied with the deposition conditions, and increases in the concentration of Ti 3+ in the films correlated with increases in film conductivity. Valence-band spectra for the a-TiO 2 films exhibited a defect-state peak below the conduction-band minimum (CBM), and increases in the intensity of this peak correlated with increases in the Ti 3+ concentration measured by EPR as well as with increases in film conductivity. The temperature dependent conduction data showed Arrhenius behavior at room temperature with an activation energy that decreased with decreasing temperature, suggesting that conduction did not occur primarily through either the valence or conduction bands. The data from all of the measurements are consistent with a Ti 3+ defect-mediated transport mode involving a hopping mechanism with a

A new dispenser and scanner system is used to create and screen Bi-M-Cu oxide arrays for cathodic photoactivity, where M represents 1 of 22 different transition and post-transition metals. Over 3000 unique Bi : M : Cu atomic ratios are screened. Of the 22 metals tested, 10 show a M-Cu oxide with higher photoactivity than CuO and 10 show a Bi-M-Cu oxide with higher photoactivity than CuBi2O4. Cd, Zn, Sn, and Co produce the most photoactive M-Cu oxides, all showing a 200-300% improvement in photocurrent over CuO. Ag, Cd, and Zn produce the highest photoactivity Bi-M-Cu oxides with a 200-400% improvement over CuBi2O4. Most notable is a Bi-Ag-Cu oxide (Bi : Ag : Cu atomic ratio of 22 : 3 : 11) which shows 4 times higher photocurrent than CuBi2O4. This material is capable of evolving hydrogen under illumination in neutral electrolyte solutions at 0.6 V vs. RHE when Pt is added to the surface as an electrocatalyst.

Amorphous titanium dioxide (a-TiO2) films formed by atomic layer deposition can serve as protective coatings for semiconducting photoanodes in water-splitting cells using strongly alkaline aqueous electrolytes. Herein, we experimentally examine...