@article{narayanan_mahajan_sukidi_bachmann_woods_dietz_2000, title={Orientation mediated self-assembled gallium phosphide islands grown on silicon}, volume={80}, ISSN={["0141-8610"]}, DOI={10.1080/01418610008212068}, abstractNote={Abstract Evolution of gallium phosphide epitaxial islands, grown on the (001), (111), (110) and (113) surfaces of Si by chemical beam epitaxy, has been investigated by p-polarized reflectance spectroscopy, transmission electron microscopy and atomic force microscopy. The growth nucleates as faceted three-dimensional islands on the (001) and (111) Si surfaces because of the polar nature of the heterointerface which increases the interfacial energy. A more two-dimensional-like growth mode is seen on the (110) and (113) surfaces which is attributed to the absence of charge build up at the GaP—Si heterointerface for these orientations, thereby reducing the interface energy. Islands grown on (001) Si become more faceted and larger in size with increase in growth temperature. This is due to a lower incubation time and enhanced atomic mobility at high temperatures. Wurtzite GaP has been observed to coexist with the zincblende polytype in some of the islands grown on (111) Si at 560°C. Arguments have been developed to rationalize these observations.}, number={3}, journal={PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES}, author={Narayanan, V and Mahajan, S and Sukidi, N and Bachmann, KJ and Woods, V and Dietz, N}, year={2000}, month={Mar}, pages={555–572} }
 @article{sukidi_bachmann_narayanan_mahajan_1999, title={Initial stages of heteroepitaxy of GaP on selected silicon surfaces}, volume={146}, ISSN={["0013-4651"]}, DOI={10.1149/1.1391736}, abstractNote={In this paper we report recent results regarding the nucleation and growth of GaP on Si(001), (111), and (113) surfaces under the conditions of pulsed chemical beam epitaxy using tertiary butylphosphine and triethylgallium as source vapors. The kinetics of nucleation and island growth were monitored in real-time by p-polarized reflectance (PR) and laser light scattering measurements. These measurements were supplemented by ex situ atomic force microscopy and high-resolution transmission electron microscopy studies. We report on the observation of an incubation time, τ i , which strongly depends on surface orientation with τ i (001) < τ i (111) < τ i (113) and, for a given surface orientation and source vapor flux, decreases with increasing substrate temperature. At time t ≥ τ i autocatalytic steps observed in the PR signal are correlated to nucleation and overgrowth of GaP nuclei. In addition, PR reveals changes during GaP growth which result in the deterioration of the previously formed perfect GaP islands that are in registry with the underlying silicon lattice. The change in growth mode may be associated with the formation of stacking faults on faceted GaP islands.}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Sukidi, N and Bachmann, KJ and Narayanan, V and Mahajan, S}, year={1999}, month={Mar}, pages={1147–1150} }
 @article{narayanan_sukidi_bachmann_mahajan_1999, title={Origins of defects in self assembled GaP islands grown on Si(001) and Si(111)}, volume={357}, ISSN={["0040-6090"]}, DOI={10.1016/S0040-6090(99)00474-5}, abstractNote={Microstructures of GaP epitaxial islands grown on Si(001) and Si(111) by chemical beam epitaxy have been investigated by transmission electron microscopy (TEM). Results indicate that planar-defect free GaP islands of sizes <20 nm can be produced at 560°C on Si(001). Some of the islands are faceted on {111} and {113} planes. Subsequent planar defect formation occurs due to stacking errors on the smaller {111} facets of GaP islands that may be P-terminated. These stacking errors are attributed to the low surface mobility on P-terminated facets. A high density of planar defects is observed in smaller islands grown on Si(001) at 420°C, a consequence of reduced atomic mobility at low temperatures that leads to {111} stacking errors. Wurtzite GaP has been observed to coexist with the zinc-blende polytype in some of the islands grown on Si(111) at 560°C.}, number={1}, journal={THIN SOLID FILMS}, author={Narayanan, V and Sukidi, N and Bachmann, KJ and Mahajan, S}, year={1999}, month={Dec}, pages={53–56} }
 @misc{narayanan_sukidi_hu_dietz_bachmann_mahajan_shingubara_1998, title={Growth of gallium phosphide layers by chemical beam epitaxy on oxide patterned (001)silicon substrates}, volume={54}, ISSN={["0921-5107"]}, DOI={10.1016/s0921-5107(98)00169-x}, abstractNote={GaP layers grown by chemical beam epitaxy in [110] channels fabricated on oxide-patterned (001)silicon substrates have been examined in cross-section by conventional and high resolution transmission electron microscopy. Results indicate that the layers are single crystalline. For the imaging conditions used, [110] cross-sectional micrographs show that growths in contact with the oxide exhibit twinning on one edge-on variant, whereas faults or twins are observed on two such variants in the layers which nucleate on the silicon substrate. Arguments for rationalizing these observations are developed, and their implications to improve the quality of the layer by confining faults or twins by the oxide sidewall are discussed.}, number={3}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Narayanan, V and Sukidi, N and Hu, CM and Dietz, N and Bachmann, KJ and Mahajan, S and Shingubara, S}, year={1998}, month={Jun}, pages={207–209} }
 @article{bachmann_sukidi_hopfner_harris_dietz_tran_beeler_ito_banks_1998, title={Real-time monitoring of steady-state pulsed chemical beam epitaxy by p-polarized reflectance}, volume={183}, ISSN={["0022-0248"]}, DOI={10.1016/s0022-0248(97)00410-7}, abstractNote={The structure in the p-polarized reflectance (PR) intensity Rp4(t) - observed under conditions of pulsed chemical beam epitaxy (PCBE) - is modeled on the basis of the four-layer stack: ambient/surface reaction layer (SRL)/epilayer/substrate. Linearization of the PR intensity with regard to the phase factor associated with the SRL results in a good approximation that can be expressed as Rp4 = Rp3 + ΔRp.Rp3 is the reflectivity of the three-layer stack ambient-epilayer-substrate. ΔRp describes the properties of the SRL. An explicit relation is derived between ΔRp(t) and the time-dependent surface concentrations ch(t) (h = 1, 2, …, N) of the constituents of the SRL, which holds for conditions of submonolayer coverage of the surface by source vapor molecules. Under conditions of low temperature PCBE at high flux, the SRL is expected to exhibit nonideal behavior, mandating replacement of the surface concentrations by activities. Also, in this case, the thickness of the SRL must be represented in terms of partial molar volumina Vh. Since the relation between ΔRp(t) and the activities of reactants, intermediates and products of the chemical reactions driving heteroepitaxial growth is non-linear, the extraction of kinetic parameters from the measured time dependence of the PR signal generally requires numerical modeling.}, number={3}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Bachmann, KJ and Sukidi, N and Hopfner, C and Harris, C and Dietz, N and Tran, HT and Beeler, S and Ito, K and Banks, HT}, year={1998}, month={Jan}, pages={323–337} }
 @article{bachmann_hopfner_sukidi_miller_harris_aspnes_dietz_tran_beeler_ito_et al._1997, title={Molecular layer epitaxy by real-time optical process monitoring}, volume={112}, DOI={10.1016/S0169-4332(96)00975-0}, abstractNote={In this paper we consider modern methods of optical process monitoring and control in the context of atomic layer epitaxy. One specific method, p-polarized reflectance spectroscopy (PRS), is chosen to assess details of layer-by-layer growth. We show that PRS monitoring under conditions of steady-state growth by pulsed chemical beam epitaxy (PCBE) can achieve the deposition of molecular layers of GaP on silicon (100) deposited with a precision of 5%, which can be improved by reducing the growth rate and increasing the period of time averaging of the reflectance data. Since in the nucleation period prior to formation of a contiguous heteroepitaxial film inhomogeneous surface chemistry and roughening complicates the modeling of the overgrowth process, advances in both experimental methods and theory are required for extending the control to non-steady-state growth conditions. Results of simultaneous single-wavelength PR monitoring and laser light scattering measurements in conjunction with atomic force microscopy studies of short period heteroepitaxial overgrowth processes are presented. The extension of PRS to the monitoring of organometallic chemical vapor deposition at higher pressures is also discussed.}, number={1997 Mar.}, journal={Applied Surface Science}, author={Bachmann, K. J. and Hopfner, C. and Sukidi, N. and Miller, A. E. and Harris, C. J. and Aspnes, D. E. and Dietz, N. A. and Tran, Hien and Beeler, S. C. and Ito, K. and et al.}, year={1997}, pages={38–47} }
 @article{dietz_sukidi_harris_bachmann_1997, title={Real-time monitoring of surface processes by p-polarized reflectance}, volume={15}, ISSN={["0734-2101"]}, DOI={10.1116/1.580712}, abstractNote={Understanding surface chemistry under steady-state epitaxial growth involving organo-metallic chemical precursor molecules is essential for optimizing growth processes. Surface-sensitive optical real-time sensor techniques are very well suited for this task as their applications are not limited to a high vacuum environment. In this article we report the combined application of the optical sensor techniques p-polarized reflectance (PR) and laser light scattering for the real-time monitoring of low temperature growth of epitaxial GaP/GaxIn1−xP heterostructures on Si(001) and GaAs(001) substrates by pulsed chemical beam epitaxy. The high surface sensitivity of PR allows to follow growth processes with submonolayer resolution during the sequential precursor exposure of the surface that causes periodic alterations in composition and thickness of a surface reaction layer (SRL), the effect of which is monitored by PR as a periodic fine structure. This fine structure is superimposed on interference oscillations, resulting from back reflection at the substrate-layer interface with increasing layer thickness. In a linear approximation of the complex four-layer stack reflectance amplitude RR4 in the phase factor Φ1, the optical response to the SRL is formulated as an additive term in the three-layer model that describes the underlying film growth process. Analytical expressions for the first derivative of the PR signal are presented and discussed with respect to the time scale of observation that allows the separation of film growth induced changes from SRL effects. The amplitude modulation and the turning points in the fine structure are assessed and compared to experimental results, showing that an average complex dielectric function of an ultrathin SRL can be quantified, independent of surface coverage.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS}, author={Dietz, N and Sukidi, N and Harris, C and Bachmann, KJ}, year={1997}, pages={807–815} }