We report, for the first time, the success of
normalGaAs
molecular layer epitaxy (MLE) using
AsH3
as an As containing gas and trimethyl‐gallium (TMG) as a Ga containing gas. Growth conditions for a single layer by layer deposition process were investigated as a function of the substrate temperature, the pressure in the growth chamber, the admittance quantity per cycle, and photoirradiation. The substrate temperature of 500°C fulfilled the conditions for a monolayer growth, where the film thickness per one cycle is saturated with the admittance quantity, at the higher temperature that increased with the TMG admittance quantity. The electrical properties of the film grown by MLE method strongly depended on the gas admittance rate, i.e., pressure in the growth chamber. The carrier density of the film proportionally decreased with increasing
AsH3
pressure and decreasing TMG pressure. However, all growth films show p‐type behavior with a carrier density of
1×1018–1020 cm−3
. Photoirradiation during the growth by a high pressure Hg lamp, Ar laser (514.5 nm), and with a doubler (257.3 nm) largely improved the surface morphology and electrical properties of the films by MLE.
The authors Phong Dai Lam and Ami Kuribayashi equally contributed to this work.Objective: To determine the optimal diagnostic criterion of dynamic contrast-enhanced MRI (DCE-MRI) for predicting salivary gland malignancy using a dynamic sequence with high temporal resolution, as well as the accuracy of this technique. Methods: The DCE-MRI findings of 98 salivary gland tumours (74 benign and 24 malignant) were reviewed. MR images were sequentially obtained at 5-s intervals for 370 s. Two parameters, peak time and washout ratio (WR) were determined from the time-signal intensity curve. The optimal thresholds of these parameters for differentiating benign and malignant tumours were determined, along with the diagnostic accuracy of the criterion using these thresholds. Results: A peak time of 150 s and a WR of 30% were identified as optimal thresholds. As the criterion for malignancy, the combination of peak time ,150 s and WR ,30% provided a sensitivity of 79% (19/24), specificity of 95% (70/74) and an overall accuracy of 91% (89/98). Three of the five false-negative cases were malignant lymphomas of the parotid gland. Conclusion: Peak time ,150 s with WR ,30% comprised the optimal diagnostic criterion in predicting salivary gland malignancy, providing a sensitivity of 79% and specificity of 95%. The use of high temporal resolution might improve the accuracy of DCE-MRI. Advances in knowledge: Although several studies have reported the usefulness of DCE-MRI in the differential diagnosis of salivary gland tumours, the specific diagnostic criteria employed have differed widely. We determined the optimal criterion and its accuracy using a dynamic sequence with high temporal resolution.
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