Structure of SiC-Quantum Wells Studied by TEM and CBED
Summary and Conclusion SiC hetero-polytypic structures have been investigated by conventional and high resolution TEM and the lattice parameters of a thin cubic stripe have been determined by CBED. For the case of the stepped substrate, nearly free of defects, about 2nm thick cubic stripes are formed within the hexagonal layer. For the case of the growth on on-axis substrates, it was demonstrated that 6H/3C as well as 4H/3C stacks are formed on 6H and 4H-SiC substrates, respectively, By CBED the lattice parameters of the cubic stripe were determined to a rhom =0.4360nm a rhom = (89.78±0.02)° demonstrating the rhombohedral distortion of the 3C stripes. It might be suggested that the result is valid also for the 2nm thick cubic stripes in the multi-quantum well structures grown on the stepped SiC substrate, although such layers are generally to thin for the lattice parameter determination by CBED. Acknowledgements The authors are indebted to Dr. A. Chuvilin for the generous scientific support during his stay as guest scientist at Jena University, thank Ch. Zaubitzer for sample preparation and acknowledge the financial support of the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 196.
Lattice Parameter Measurements of 3C-SiC Thin Films Grown on 6H-SiC(0001) Substrate Crystals
The lattice parameters of 3C-SiC thin films epitaxially grown on 6H-SiC(0001) substrate crystals have been precisely determined by using high resolution x-ray diffraction methods. Reciprocal space maps recorded around symmetrical and asymmetrical x-ray reflections revealed a pseudomorphic growth of the thin film in relation to the substrate lattice, whereas perpendicular to the surface the interplanar spacing of the lattice planes differ slightly ∆d/d = 8.7⋅10. This implicates inherent thin film strain (e) and stress (σ ) components. The in-plane components are found to be ei = 4.8⋅10 and σi = 2.26⋅10 N/m, whereas perpendicular to the surface the thin film strain component is found to be e^ = 2.8⋅10. Introduction Silicon Carbide (SiC) occurs in many polytypes which differ in their periodic stacking sequences of hexagonal and cubic Si-C bilayers. The SiC lattice parameters differ slightly from polytype to polytype [1]. Using x-ray diffraction methods the lattice parameters of 4Hand 6H-SiC single crystal wafers [2] have been determined precisely (Table 1). Unfortunately, large 3C-SiC single crystals are not available. However, 3C-SiC thin films can be easily grown and used to derive the lattice parameters of compact 3C-SiC crystals if one takes the inherent stress, induced by the thin film growth, into account. The 3C-SiC thin films (thickness ≈ 1.2 μm) were grown by solid-source molecular beam epitaxy on (0001)-oriented on-axis 6H-SiC crystal wafers at deposition temperatures between 780°C to 950°C and with growth rates between 30 nm/h to 120 nm/h [3]. High resolution x-ray diffraction of 3C-SiC thin films Although the lattice parameters of the different SiC polytypes differ only slightly, the x-ray diffraction pattern showed, close to each other but well separated, so-called family reflections of the 3C-SiC thin film and 6H-SiC substrate. Using the well known 6H-SiC bulk crystal values (Table 1) as a reference, we could determine the lattice parameters of the 3C-SiC thin films with a corresponding accuracy of 10 for Da/a and 10 for Dc/c. Reciprocal space maps recorded around symmetrical and asymmetrical x-ray reflections (Fig. 1) revealed a pseudomorphous growth of the 3C-SiC thin films in relation to the substrate lattice (Fig. 2). There is no difference between the lateral interplanar spacing of the lattice planes, but perpendicular to the surface their interplanar spacing differ by ∆d/d = 8.7⋅10. The growth direction of the 3C-SiC thin film was found to be [111] with respect to the surface normal. Silicon Carbide and Related Materials (2001). 319-322 319
Atomistic insight into novel co-delivery of doxorubicin and paclitaxel using fullerene modified by dimethyl acrylamide trimethyl chitosan: A computational study

 Background: The distribution of drugs could not be controlled in the conventional drug delivery system. This has led to the development of a smart nanoparticle-based drug delivery system, known as smart drug delivery systems. In cancer research, novel biocompatible nanocarriers have received much attention for various ranges of anticancer drugs.In the current study, the effect of a novel co-polymer "dimethyl acrylamide-trimethyl chitosan" was investigated on drug delivery of doxorubicin and paclitaxel utilizing modified fullerene nanocarrier. This study was performed via molecular dynamics simulation based on acidic pH sensitivity of the cancer microenvironment. Furthermore, hydrogen bonds, diffusion coefficient, gyration radius, and drug-carrier interaction energies were investigated here. Interestingly, a simultaneous pH and temperature-sensitive system was proposed for paclitaxel and doxorubicin for a co-polymer. A pH-sensitive and temperature-sensitive copolymer was used based on trimethyl chitosan and dimethyl acrylamide, respectively. In such a dualistic approach, co-polymer makes an excellent option to have two properties in one bio-polymer. Results: The results suggest the dramatic and indisputable role of the co-polymer in the release of doxorubicin and paclitaxel in cancerous tissues, as well as an increased biocompatibility and drug uptake in a neutral state. The validation test was performed by repeated simulations of a similar article. The results are very close to those of the reference paper .Conclusions: Overall, conjugated fullerene and dimethyl acrylamide-trimethyl chitosan (DMAA-TMC) as carriers can be a good proposition for loading, delivery, and release of anti-cancer drugs based on a pH/temperature-sensitive smart drug delivery system.