The properties of electron−hole (e−h) pairs generated in a working poly(3-hexylthiophene) (P3HT) diode are investigated by electrically detected magnetic resonance (EDMR) techniques. The EDMR intensity is shown to increase with increasing density of injected electrons for a given hole density, demonstrating that the EDMR signal arises from an e−h pair. The EDMR spectrum consists of two Gaussian curves, one of which gives a g-value very similar to that of hole carriers, suggesting that the EDMR spectrum is given by the sum of electron spin resonance (ESR) spectra from hole and electron carriers forming e−h pairs. Bias-dependent correlation between carriers and e−h pairs under diode operation is examined directly from independent measurements of near-infrared (NIR) spectroscopy for carriers and EDMR for e−h pairs. When the bias is increased to above a threshold, the EDMR signal is strongly reduced despite a gradual increase in the NIR signals, providing evidence that the e−h pairs are dissociated by an electric field in the bias region. Because of this property of the pair, the correlation between the carriers and e−h pairs inside the diode changes depending on the bias magnitude: the carriers and e−h pairs coexist or only the carriers exist. The e−h pair is presumed to be formed across different lamellae because of the crystalline phase of the P3HT film. Although the intensity of the EDMR signal from the interlamellar e−h pair is small, the intensity increases substantially when the sample is exposed to air, suggesting the formation of a magnetoreactive species that incorporates oxygen.

We studied initial Cu overlayer formation on the Ni͑110͒ surface by scanning tunneling microscopy ͑STM͒ in an ultrahigh vacuum. Initially, deposited Cu displaces the top Ni layer, forming two-dimensional Cu-Ni alloy on the substrate. The Cu atom embedded into the top layer was depressed in the STM image. The depression due to the lack of Ni 3d-derived surface local density of states was confirmed by the first-principles calculation. Ni atoms squeezed out from the top substrate layer agglomerated in the anisotropic Ni island along the close-packed ͓110͔ direction. Further Cu deposition resulted in a Cu-Ni mixed island. Quantitative measurement of the Cu fraction on the substrate showed that 0.71Ϯ 0.04 of deposited Cu was embedded in the top Ni layer, whereas significant Cu enrichment was seen on the island.

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