Electron spin is fundamental in electrical and optical properties of organic electronic devices. Despite recent interest in spin mixing and spin transport in organic semiconductors, the actual spin coherence times in these materials have remained elusive. Measurements of spin coherence provide impartial insight into spin relaxation mechanisms, which is significant in view of recent models of spin-dependent transport and recombination involving high levels of spin mixing. We demonstrate coherent manipulation of spins in an organic light-emitting diode (OLED), using nanosecond pulsed electrically detected electron spin resonance to drive singlet-triplet spin Rabi oscillations. By measuring the change in photovoltaic response due to spin-dependent recombination, we demonstrate spin control of electronic transport and thus directly observe spin coherence over 0.5 s. This surprisingly slow spin dephasing underlines that spin mixing is not responsible for magnetoresistance in OLEDs. The long coherence times and the spin manipulation demonstrated are crucially important for expanding the impact of organic spintronics.

Pulsed electrically detected magnetic resonance of phosphorous (31P) in bulk crystalline silicon at very high magnetic fields (B0>8.5 T) and low temperatures (T=2.8 K) is presented. We find that the spin-dependent capture and reemission of highly polarized (>95%) conduction electrons by equally highly polarized 31P donor electrons introduces less decoherence than other mechanisms for spin-to-charge conversion. This allows the electrical detection of spin coherence times in excess of 100 mus, 50 times longer than the previous maximum for electrically detected spin readout experiments.

In order to determine the proper multivariate calibration model, it is necessary to select the number of respective basis vectors (latent vectors, factors, etc.) when using principal component regression (PCR) or partial least squares (PLS). These values are commonly referred to as the prediction rank of the model. Comparisons between PCR and PLS models for a given data set are often made with the prediction rank to determine the more parsimonious model, ignoring the fact that the values have been obtained using different basis sets. Additionally, it is not possible to use this approach for determining the prediction rank of models generated by other modeling methods such as ridge regression (RR). This paper presents measures of effective rank for a given model that can be applied to all modeling methods, thereby providing inter-model comparisons. A definition based on the regression vector norm and is compared with two alternative forms from the literature. With a proper definition of effective rank, a better assessment of degrees of freedom for statistical computations is possible. Additionally, the true nature of variable selection for improved parsimony can be properly assessed. Spectroscopic data sets are used as examples with PCR, PLS and RR.

An experimental study on the nature of spin-dependent excess charge carrier transitions at the interface between (111) oriented phosphorous doped ([P]≈ 10 15 cm −3 ) crystalline silicon and silicon dioxide at high magnetic field (B 0 ≈ 8.5T) is presented. Electrically detected magnetic resonance (EDMR) spectra of the hyperfine split 31 P donor electron transitions and paramagnetic interface defects were conducted at temperatures in the range 3 K≤ T ≤12 K. The results at these previously unattained (for EDMR) magnetic field strengths reveal the dominance of spin-dependent processes that differ from the previously well investigated recombination between the 31 P donor and the P b state, which dominates at low magnetic fields. While magnetic resonant current responses due to 31 P and P b states are still present, they do not correlate and only the P b contribution can be associated with an interface process due to spin-dependent tunneling between energetically and physically adjacent P b states. This work provides an experimental demonstration of spin-dependent tunneling between physically adjacent and identical electronic states as proposed by Kane for readout of donor qubits. 71.55.Cn, 73.40.Qv Phosphorus doped crystalline silicon (c-Si:P) is one of the most widely utilized semiconductor materials, with applications ranging from conventional microelectronics 1 to proposed and presently widely investigated concepts for spintronics 2 and spin-based quantum information processing (QIP) 3 . Silicon based spin-QIP and spintronics concepts aim to utilize the comparatively weak spin-orbit coupling present in this material, and the correspondingly very long spincoherence times 2,3 , as well as the impact of spin-selection rules on electronic transitions which can be used for spin readout 4 . Most of these applications involve electrical transport and spin manipulation at or near the silicon-silicon dioxide (SiO 2 ) interface, making the understanding of spin processes in this region extremely important. Numerous studies of spin-dependent transport and recombination at the interface between c-Si:P and SiO 2 have recently been undertaken, with the aim of identifying and understanding these mechanisms 5,6,7 , and showing that they can be utilized for the observation of very small ensembles of donors 8 and coherent spin motion 7,9 . Additionally, spin dependent transport in two dimensional electron gases at the c-Si/SiO 2 interface has been demonstrated 10,11 . However, no systematic study of such processes at high magnetic field has been conducted to date, with the only data at magnetic fields B 0 > 400 mT given by a single electrically detected magnetic resonance (EDMR) spectrum recorded at B 0 = 7.1 T and a temperature T = 4 K 12 .In the following, a systematic investigation of the spin dependent processes at the interface between c-Si:P and SiO 2 are presented for high magnetic fields (B 0 ≈ 8.5 T) at temperatures in the range 3 K≤ T ≤12 K.We show that the dominant spin-dependent recombination mechanism at low magnet...

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