Using a reduced pressure-chemical vapor deposition cluster tool, we have studied the growth kinetics of Si and SiGe and the n-type and p-type doping of Si with both silane and dichlorosilane ...chemistries. As far as Si is concerned, a conventional behavior is found for both gases, i.e. a low-temperature region where the Si growth rate is limited by the desorption of the H atoms from the growing surface (activation energy equal to 47
kcal/mol), and a high-temperature region, where the Si growth rate is mainly piloted by the incoming flow of SiH
4 or SiH
2Cl
2 (activation energy of 4
kcal/mol). The incorporation of B in Si is linear with the B
2H
6 flow (p-type doping of Si), achievable with an overall 9×10
16–4×10
19
cm
−3 B ions concentration range. There is a sub-linear dependency of the P incorporation into Si with the PH
3 flow (n-type doping of Si). A 2×10
16–9×10
18
cm
−3 P ions concentration range can be reached with both silicon gas sources. The growth rate of boron-doped Si is virtually unaffected by increasing B
2H
6 flow. Meanwhile, the growth rate of phosphorous-doped Si steadily drops when the PH
3 flow is increased. As far as the SiH
4+GeH
4 chemistry is concerned, the Ge concentration
x in the SiGe film obeys at 650°C the following law as a function of the F(GeH
4)/F(SiH
4) mass flow ratio:
x/(1−
x)=2.7(F(GeH
4)/F(SiH
4)). For the SiH
2Cl
2+GeH
4 chemistry,
x is linked at 750°C to the F(GeH
4)/F(SiH
2Cl
2) mass flow ratio through the following relationship:
x
2/(1−
x)=0.55(F(GeH
4)/F(SiH
2Cl
2)). The SiGe growth rate increases strongly with an increasing GeH
4 flow, with no apparent influence of the actual SiH
4 or SiH
2Cl
2 flow. This is attributed to an increased hydrogen desorption caused by the presence of Ge atoms on the growing surface that frees nucleation sites for the incoming Ge and Si atoms.
We have studied the impact of various H2 bakes (in-between 750 and 850 deg C, this for durations in-between 15 and 120 s) on the structural properties of 16 nm thick sSi layers grown on top of ...polished SiO.7Ge0.3 and SiO.6Ge0.4 virtual substrates (VSs) after an 'HF-last' wet cleaning. Those stacks have been characterized afterwards thanks to tapping mode-atomic force microscopy (AFM), surface light scattering (haze measurements), secondary ions mass spectrometry and Secco defect revelation. A definite oxygen contamination peak at the sSi/SiGe interface was associated to 750 deg C, 120 s H2 bakes. The resulting sSi layers were heavily defected and rough. By contrast, temperatures superior or equal to 800 deg C yielded contamination-free interfaces. No clear impact of the H2 bake temperature (800 deg C) and/or duration on the threading dislocation density and the 'line' defect linear density was evidenced. Higher temperatures and longer bakes yielded rougher surfaces, however. The best compromise seemed to be {850 deg C, 15 s} H2 bakes. For such bakes, the surface root mean square surface roughness was in-between 0.1 and 0.2 nm only (10 mumX10 mum AFM images).
To investigate the spatial and temporal pattern of cortical responses evoked by deep brain stimulation (DBS) of the subthalamic nucleus (STN) and ventral intermediate nucleus of the thalamus (VIM).
...We investigated 7 patients suffering from Essential tremor (ET) and 7 patients with Parkinson's Disease (PD) following the implantation of DBS electrodes (VIM for ET patients, STN for PD patients). Magnetoencephalography (MEG) was used to record cortical responses evoked by electric stimuli that were applied via the DBS electrode in trains of 5 Hz. Dipole fitting was applied to reconstruct the origin of evoked responses.
Both VIM and STN DBS led to short latency cortical responses at about 1 ms. The pattern of medium and long latency cortical responses following VIM DBS consisted of peaks at 13, 40, 77, and 116 ms. The associated equivalent dipoles were localized within the central sulcus, 3 patients showed an additional response in the cerebellum at 56 ms. STN DBS evoked cortical responses peaking at 4 ms, 11 ms, and 27 ms, respectively. While most dipoles were localized in the pre- or postcentral gyrus, the distribution was less homogenous compared to VIM stimulation and partially included prefrontal brain areas.
MEG enables localization of cortical responses evoked by DBS of the VIM and the STN, especially in the sensorimotor cortex. Short latency responses of 1 ms suggest cortical modulation which bypasses synaptic transmission, i.e. antidromic activation of corticofugal fiber pathways.
•Cortical responses evoked by VIM or STN DBS can be precisely described using MEG.•Both STN and VIM DBS primarily evoke cortical responses within the sensorimotor region.•Short latency responses of 1 ms both observed in VIM and STN DBS suggest antidromic activation of corticofugal fibers.
The pathogenesis of testicular germ cell tumours (GCTs) is potentially influenced by high-energy nutrition during infancy. As adult height is a proxy for childhood nutrition, we investigated the role ...of nutrition in GCT pathogenesis by comparing stature of patients with healthy men. In a matched case-control study, 6415 patients with GCT were compared with healthy army conscripts (1:6 matching modus) with regard to height (cm) and body mass index (BMI; kg/m(2)). Statistical analysis involved tabulation of descriptive height measures and BMI. Conditional logistic regression models were used to quantify the association of GCT with height, with odds ratios (OR) adjusted for BMI. The literature was searched for studies on stature in GCT patients. Body size is significantly associated with risk of GCT, very tall men (>195 cm) having a GCT risk of OR=3.35 (95% confidence intervals (CI): 2.88-3.90; adjusted). Short stature is protective (OR=0.798; 95% CI: 0.68-0.93). Both histologic subgroups are associated with tallness. Of 16 previous reports, 7 were confirmative, 5 had null and 4 equivocal results. The association of stature with GCT risk accords with the nutrition hypothesis of GCT. This study expands the current view of GCT tumorigenesis by suggesting that high-calorie intake in childhood promotes GCT precursors originating in utero.
To determine the efficacy of first-line sequential high-dose VIP chemotherapy (HD-VIP) in patients with primary mediastinal nonseminomatous germ cell tumours (GCT), 28 patients were enrolled on a ...German multicentre trial. High-Dose VIP chemotherapy consisted of 3-4 cycles of dose-intensive etoposide and ifosfamide plus cisplatin, q22days, each cycle followed by autologous peripheral blood stem cell transplantation plus granulocyte-colony stimulating factor (G-CSF) support. One cycle of standard-dose VIP was applied to harvest peripheral blood stem cells. Ten patients had mediastinal involvement as the only manifestation (36 %), 18 of 28 patients had additional metastatic sites, such as lung (n=17; 61%), liver (n=7; 25%), bone (n=5; 18%), lymph nodes (n=3; 11%) and CNS (n=3; 11%). Median follow-up was 43 months (range, 7-113) for all patients and 52 months (range, 22-113) for surviving patients. Nineteen of 28 patients obtained a disease-free status; 11 with HD-VIP alone and eight with adjunctive surgery. In addition, one of the four patients with marker negative partial remission after HD-VIP without resection of residual masses is currently alive. Two patients developed recurrence of GCT or teratoma. Two patients have died due to an associated haematologic disorder. The 2-year progression-free survival and overall survival rates are 64 and 68%, respectively. This report represents a subgroup analysis of 28 patients with mediastinal nonsemina within the German first-line study for 'poor prognosis' GCT. Compared to data of an international database analysis including 253 patients with mediastinal nonseminoma treated with conventional chemotherapy, the results may indicate that HD-VIP results in an approximately 15% survival improvement.
Well characterised sources of thermal radiation are essential for photometry, radiometry, and thermometry. They serve as reference radiators for the calibration of detectors and radiance sources. ...Thermal radiation sources are advantageous for this purpose compared to other radiance sources such as lamps or LEDs because they possess a continuous spectrum of the emitted spectral radiance, which, for blackbody sources, can be calculated analytically using Planck’s law of radiation.
For application in thermometry, blackbody sources starting from temperatures near absolute zero to temperatures up to 3000
∘C are needed for the calibration of radiation thermometers. For application in photometry and radiometry high intensity sources of radiation in the visible and UV region of the optical spectrum were required. This latter requirement is met by blackbody sources at temperatures well above 2000
∘C. An ideal reference source should always emit the same amount of radiation at any time of use. This is realised by fixed-point radiators. Such radiators are based on a phase transition of a substance, at high temperatures the melting and freezing points of metals. However, current metal fixed-points are limited to relatively low temperatures. In the present work innovative techniques necessary for research into high-temperature thermal radiation sources are developed and thoroughly described. Starting with variable temperature blackbody sources the techniques required are: Precise apertures determination and detailed characterisation of the applied optical detectors.
The described techniques are then used to undertake research into the development of high-temperature fixed-points above the copper fixed-point for application in photometry, radiometry, and thermometry. Applying these sophisticated techniques it was shown that these new high-temperature fixed-points are reproducible and repeatable to better than 100 mK at temperatures up to nearly 3200 K. Finally, a forward look is given that shows the potential of such fixed-points for improving traceability and accuracy in photometry, radiometry, and thermometry. This work forms the foundation for accurate and practical applications of high-temperature fixed-point sources and sets the international benchmark for measurement techniques in photometry, radiometry, and thermometry. This work will open the use of the novel high-temperature fixed-points in an improved International Temperature Scale and will significantly improve and ease the realisation and dissemination of the SI base unit candela, significantly reducing the uncertainty for industrial measurements in these fields.
In biological systems, the task of computing a gait trajectory is shared between the biomechanical and nervous systems. We take the perspective that both of these seemingly different computations are ...examples of physical computation. Here we describe the progress that has been made toward building a minimal biped system that illustrates this idea. We embed a significant portion of the computation in physical devices, such as capacitors and transistors, to underline the potential power of emphasizing the understanding of physical computation. We describe results in the exploitation of physical computation by (1) using a passive knee to assist in dynamics computation, (2) using an oscillator to drive a monoped mechanism based on the passive knee, (3) using sensory entrainment to coordinate the mechanics with the neural oscillator, (4) coupling two such systems together mechanically at the hip and computationally via the resulting two oscillators to create a biped mechanism, and (5) demonstrating the resulting gait generation in the biped mechanism.
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