Ion Implantation and Misfit Dislocation Formation in P/P+Silicon

Abstract

We determined that self implantation of pseudomorphically strained silicon epitaxial layers greatly attenuates strain relaxation. We employed highly boron doped 150 mm diameter silicon with a nominally un-doped, 2.5 μm thick epitaxial layer (p/p+). The compressively strained layer (mismatch ≈ 1.5 × 10−4) showed inhomogeneous relaxation after epitaxial growth, with misfits forming only near the wafer periphery. High temperature rapid thermal annealing was employed after ion implantation to study misfit dislocation nucleation and glide. Our results suggest that low dose ion implantation has a potential to reduce misfit dislocation propagation and nucleation in epitaxial thin films.

Ultrasound-responsive gene-activated matrices for osteogenic gene therapy using matrix-assisted sonoporation

“…The in vivo ectopic bone formation data obtained above suggest that this GAM could play a role in approaches involving the latter. The data demonstrated that the highest frequency of bone formation (100%) was delivered with MAS and this is in line with previous studies showing that sonoporation can significantly increase the frequency of successful gene delivery and associated bone formation in vivo (Feichtinger et al, 2014a). The novel outcome of the current study regarding the significantly (5.4-to 16.4-fold) increased yields of bone volumes attainable with MAS ( Figure 4) compared to all other standard treatment modalities (passive GAM and sonoporation) is furthermore superior to those from previous studies by us and other groups in which multiple rounds of sonoporation and higher DNA doses were necessary for tissue formation (Feichtinger et al, 2014a;Osawa et al, 2009).…”

“…The data demonstrated that the highest frequency of bone formation (100%) was delivered with MAS and this is in line with previous studies showing that sonoporation can significantly increase the frequency of successful gene delivery and associated bone formation in vivo (Feichtinger et al, 2014a). The novel outcome of the current study regarding the significantly (5.4-to 16.4-fold) increased yields of bone volumes attainable with MAS ( Figure 4) compared to all other standard treatment modalities (passive GAM and sonoporation) is furthermore superior to those from previous studies by us and other groups in which multiple rounds of sonoporation and higher DNA doses were necessary for tissue formation (Feichtinger et al, 2014a;Osawa et al, 2009). In previous studies using a cell and matrix-free sonoporation-based approach it was necessary to use 100 μg of DNA and an ultrasound energy density of 90-600 J/cm 2 whereas here, 6.5 μg of DNA and an ultrasound energy density of 30 J/cm 2 were used (Feichtinger et al, 2014a).…”

“…The inducible and constitutive single-vector BMP2/7 coexpression plasmids, pTetON-BMP2/7 and pVAX1-BMP2/ 7 have been described previously (Feichtinger et al, 2014a). The reporter plasmid pCMV-Luc, encoding the firefly luciferase gene under the control of the CMV promoter, was supplied by PlasmidFactory GmbH & Co (Bielefeld, Germany).…”

“…Having demonstrated that ultrasound could be used to facilitate gene transfer and expression in 3D matrices without any negative impact on cell viability using high cell numbers with the new polymeric microbubbles, it was decided to use the approach to enable gene transfer of therapeutic plasmids coexpressing BMP2 and BMP7 into C2C12 cells and determine whether or not this would result in osteogenic differentiation. To this end, the effect of microbubbles and ultrasound on the delivery of the BMP2/7-coexpressing plasmid constructs (Feichtinger et al, 2014a) (either pTetON-BMP2/7 or pVAX1-BMP2/ 7) and resultant osteogenic differentiation was examined in 3D matrices containing C2C12 cells. Where the inducible pTetON-BMP2/7 plasmid was used, the inducer doxycycline was added to the system.…”

“…With this end in mind, it was recently demonstrated that ultrasound-mediated, microbubble-enhanced gene delivery could be achieved with target cells embedded in fibrin/collagen hydrogel matrices in vitro (Nomikou et al, 2016). In associated studies, it was demonstrated that, should it prove necessary, an additional level of control at the transcriptional level could be incorporated into the expression plasmids to enable tight control of the therapeutic transgene expression window after delivery by ultrasound-mediated, microbubble-enhanced gene transfer (Feichtinger et al, 2014a).…”