Selective area heteroepitaxy of GaSb on GaAs (001) for in-plane InAs nanowire achievement.

The growth of in-plane GaSb nanotemplates on a GaAs (001) substrate is demonstrated combining nanoscale patterning of the substrate and selective area heteroepitaxy. The selective growth of GaSb inside nano-stripe openings in a SiO2 mask layer is achieved at low temperature thanks to the use of an atomic hydrogen flux during the molecular beam epitaxy. These growth conditions promote the spreading of GaSb inside the apertures and lattice mismatch accommodation via the formation of a regular array of misfit dislocations at the interface between GaSb and GaAs. We highlight the impact of the nano-stripe orientation as well as the role of the Sb/Ga flux ratio on the strain relaxation of GaSb along the [110] direction and on the nanowire length along the [1-10] one. Finally we demonstrate how these GaSb nanotemplates can be used as pedestals for subsequent growth of in-plane InAs nanowires.

Impact of P/In flux ratio and epilayer thickness on faceting for nanoscale selective area growth of InP by molecular beam epitaxy.

The impact of the P/In flux ratio and the deposited thickness on the faceting of InP nanostructures selectively grown by molecular beam epitaxy (MBE) is reported. Homoepitaxial growth of InP is performed inside 200 nm wide stripe openings oriented either along a [110] or [1-10] azimuth in a 10 nm thick SiO2 film deposited on an InP(001) substrate. When varying the P/In flux ratio, no major shape differences are observed for [1-10]-oriented apertures. On the other hand, the InP nanostructure cross sections strongly evolve for [110]-oriented apertures for which (111)B facets are more prominent and (001) ones shrink for large P/In flux ratio values. These results show that the growth conditions allow tailoring the nanocrystal shape. They are discussed in the framework of the equilibrium crystal shape model using existing theoretical calculations of the surface energies of different low-index InP surfaces as a function of the phosphorus chemical potential, directly related to the P/In ratio. Experimental observations strongly suggest that the relative (111)A surface energy is probably smaller than the calculated value. We also discuss the evolution of the nanostructure shape with the InP-deposited thickness.

Influence of nanoscale faceting on the tunneling properties of near broken gap InAs/AlGaSb heterojunctions grown by selective area epitaxy.

We report on the selective area molecular beam epitaxy of InAs/AlGaSb heterostructures on a GaSb (001) substrate. This method is used to realize Esaki tunnel diodes with a tunneling area down to 50 nm × 50 nm. The impact of the size reduction on the peak current density of the diode is investigated, and we show how the formation of the InAs facets can deeply affect the band-to-band tunneling properties of the heterostructure. This phenomenon is explained by the surface-dependent incorporation of Si dopant during growth.

[Clinical and electrophysiological study of sensory penile alterations. A prospective study of 44 cases]. / Analyse clinique et neurophysiologique des troubles de la sensibilité pénienne. Étude prospective de 44 cas.

OBJECTIVE: To precise clinical presentations, pathophysiology and etiologies of penile sensory alteration. METHODS: Forty-four patients with penile sensory dysfunction underwent clinical and electrophysiological testing with electromyography of bulbocavernosus muscles, study of sacral reflex latencies, somatosensory cortical responses following stimulation of the dorsal nerve of the penis, sensory velocity of the dorsal nerve and pudendal nerve terminal sensory latencies. RESULTS: Penile anesthesia was observed in six (13%) patients, loss of sensibility in 34 (77%), paresthesia in four (9%). Erectile dysfunction was noted in 19 (43%) patients, hypo-orgasmia in seven (16%), cold glans penis sensation in four and loss of spatial sensation during intercourse in three (7%). Abnormalities of electrophysiological perineal testing were observed in 17 (38%) patients. In 27 (62%) cases, no alteration of electrophysiological testing was observed. In 17 (38%) patients, a specific aetiology was founded by means nerve palsy during orthopedic surgery in five cases, entrapment neuropathy following byking in nine cases, two La Peyronie diseases and one diabetes mellitus. CONCLUSION: In the current series, the prevalence of neuropathy of the dorsal nerve of the penis (that can determine a loss of sensibility) was 40%.

[Contribution of somatosensory evoked potentials in the surveillance of the spinal cord during spinal surgery]. / Apports des potentiels évoqués somesthésiques dans la surveillance médullaire au cours de la chirurgie rachidienne.

This study shows the results obtained in 51 patients, children and adolescents by monitoring somatosensory evoked potentials during spinal surgery: Cotrel-Dubousset instrumentation, surgical anterior correction by plating, spondylolisthesis and hemivertebra surgery. The recordings were made in preoperative, peroperative and postoperative periods; the electro-physiological and anaesthetic conditions allowed us to obtain reliable recordings. Analysis of the peroperative somatosensory evoked potentials showed significant differences in latencies, but also in amplitudes and morphology during distraction in scoliosis or spondylolisthesis. These impairments gradually improved and recovered their normal values at the end of the operation. The impairments were, with equal correction, 4 times more important in Cotrel-Dubousset instrumentation than in surgical anterior correction by plating. In 3 cases, the modifications observed during instrumentation led the surgeon to change his operative behavior avoiding certainly a postoperative neurological disorder. The correlation between the neurological troubles and the impairments of the potentials allowed us to define alarm criteria, and if they persist the wake-test becomes necessary.