Nb+Al) codoped rutile TiO 2 ceramics with nominal composition Ti 4+ 0.995 Nb 5+ 0.005y Al 3+ 0.005z O 2 , z = (4−5y)/3 and y = 0.4, 0.5, 0.6, 0.7, and Ti 4+ 0.90 Nb 5+ 0.05 Al 3+ 0.05 O 2 have been synthesized. The resultant samples in ceramic pellet form exhibit a colossal dielectric permittivity (>∼10 4 ) with an acceptably low dielectric loss (∼10 −1 ) after optimization of the processing conditions. It is found that a conventional surface barrier layer capacitor (SBLC) effect, while it contributes significantly to the observed colossal permittivity, is not the dominant effect. Rather, there exists a subtle chemical compositional gradient inward from the pellet surface, involving the concentration of Ti 3+ cations gradually increasing from zero at the surface without the introduction of any charge compensating oxygen vacancies. Instead, well-defined G r ± 1 / 3 [011]* satellite reflections with the modulation wave-vector q = 1 / 3 [011] r * and sharp diffuse streaking running along the G r ± ε[011]* direction from electron diffraction suggest that the induced additional metal ions appear to be digested by a locally intergrown, intermediate, metal ion rich structure. This gradient in local chemical composition exists on a scale up to ∼ submillimeters, significantly affecting the overall dielectric properties. This work suggests that such a controllable surface compositional gradient is an alternative method to tailor the desired dielectric performance.

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We present the results of electrically-detected magnetic resonance (EDMR) experiments on ion-implanted Si:P nanostructures at 5 K, consisting of high-dose implanted metallic leads with a square gap, in which Phosphorus is implanted at a non-metallic dose corresponding to 10 17 cm −3 . By restricting this secondary implant to a 100 nm × 100 nm region, the EDMR signal from less than 100 donors is detected. This technique provides a pathway to the study of single donor spins in semiconductors, which is relevant to a number of proposals for quantum information processing. The ability to spectroscopically study the spin properties and interactions of a small number of donors in semiconductors has many applications such as the storage of classical information in nuclear or electronic spins, 1 and is relevant to a number of proposals 2,3 related to quantum information processing (QIP). In particular, the construction of QIP hardware utilizing Si:P has been discussed by Kane 4 and Hollenberg. 5 In this context, the ultimate task is the detection of the electron or nuclear spin state of single P donors.

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