Investigation of Surface Phase Layers on GaAs after Selective Chemical Etching

Normal 0 false false false RU X-NONE X-NONE The combination of methods of voltammetry, Raman spectroscopy, and X-ray reflectometry for the first time has been applied for the more comprehensive investigation of interfacial boundaries of GaAs, i.e. determination of phase distribution and thickness of the phase layers. The conditions for the formation of elemental arsenic on a GaAs surface in the process of selective dissolution are discussed. The stability of interfacial boundaries in air has also been studied. The investigations have shown that air storage lead to the oxidation of formed As0 and reorganization of GaAs interfacial boundary accompanied by the formation of Ga2O3 and As0 as a result of a reaction between As2O3 and GaAs. The results on interfacial boundaries composition were found to be correlated with the theoretical data. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Обычная таблица"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

Improvement of Atomic-Layer-Deposited Al2O3/GaAs Interface Quality through a Novel Sulfuration Method

The absence of stable oxide/GaAs interface greatly holds back the step of GaAs-based MOSFETs fabrication. In this letter, we report on the chemical passivation of n-type GaAs surface by introducing a new sulfuration method. X-ray photon-electron spectroscopy (XPS) analyses indicate that most GaAs native oxides and elemental arsenic (As) can be more effectively removed by treating the GaAs surface in CH3CSNH2solution compared to the traditional (NH4)2S solution. Capacitance-Voltage characteristics of the CH3CSNH2treated MOS capacitors also presents reduced interfacial layer and equivalent oxide thickness which are well consisted with the conclusion obtained by XPS.

Elemental Arsenic Levels in Plasma, Cellular and Tissue Compartments After Oral Arsenic Trioxide Maintenance Treatment: Implications On Long-Term Safety.

Abstract 2064 Poster Board II-41 Background. Arsenic trioxide (As2O3) is a standard medication in the management algorithm of patients with acute promyelocytic leukemia (APL). With the advent of oral As2O3, outpatient treatment, convenient dosing and long-term post-remission maintenance therapy have become possible. The pharmacokinetics, efficacy and safety profile of short-term oral As2O3 therapy are well-defined. With prolonged oral-As2O3 therapy, possible accumulation of elemental arsenic and its possible long-term side effects must be determined. Materials and methods. Paired peripheral blood (PB) and bone marrow (BM) (aspirate and trephine biopsy) specimens were prospectively collected as part of an oral-As2O3 treatment protocol of patients. The samples were separated into plasma (P), white blood cell (WBC) and red blood cell (RBC) fractions. Elemental arsenic was measured by inductively coupled plasma-mass spectrometry (ICP-MS, ELAN DRCplus 6100, PerkinElmer-SCIEX, Canada) after dilution with 2% nitric acid +/– 3% methanol. Bone marrow trephine biopsies were dried at 65°C overnight, completely digested with acid, and diluted to appropriate concentrations. Results. There were 15 male and 11 female APL patients. Seven WBC specimens could not be analyzed due to inadequate material. Specimens were collected at 1 month (Group 1), 2–12 months (Group 2) and 24–41 months (Group 3) after cessation of oral-As2O3 treatment. The median cumulative dose of oral-As2O3 was 1980 (560–3680) mg. As control, samples were obtained from 12 anonymous individuals, whose specimens were collected as part of their diagnostic evaluations. These controls had no known medicinal exposure to arsenic. The mean elemental arsenic levels in the specimens were shown below. Elemental arsenic levels in group 1 were significantly higher than groups 2 and 3 in all specimens tested. However, groups 2 and 3 were comparable to controls, indicating that arsenic was rapidly excreted once oral-As2O3 treatment was stopped. In group 1 patients, all specimens tested showed comparable arsenic levels. In group 2 patients, arsenic levels were significantly higher in BM–WBC (but not PB-WBC) as compared with PB-P and BM-P (p=0.043 for both). In group 3 patients, all cellular specimens tested showed comparable arsenic levels to plasma levels. Conclusion. Immediately after cessation of treatment when plasma arsenic level was still high, elemental arsenic was distributed comparably in different compartments. However, when plasma arsenic levels started to decline, preferential concentration of arsenic occurred in the cellular compartments. This could be related to transfer of arsenic in bones to the developing hematopoietic cells in the marrow milieu. Finally, two or more years after cessation of As2O3 therapy, elemental arsenic levels returned to control levels; a reassuring observation that long-term arsenic accumulation did not take place when oral-As2O3 was used therapeutically during a finite period of time. Disclosures: Off Label Use: Oral arsenic trioxide is a novel preparation or arsenic trioxide currently under consideration for registration in Hong Kong for APL treatment. The University of Hong Kong holds the patent for the product.

Arsenic Trioxide Entered Cerebrospinal Fluid with the Help of Mannitol Overwhelm the Meningeal Relapse of Acute Promyelocytic Leukemia.

Background and objective Central nervous system (CNS) relapse of acute promyeloytic leukemia (APL) is increasingly reported after treatment with all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3), the optimal therapy for these cases remains unclear. As2O3 highly effective in APL marrow relapse, but its efficacy in APL CNS relapse is undefined. Recent researches showed that little As2O3 could pass through the intact blood- brain-barrier (BBB), which limits its use in prevention and treatment of central nervous system acute promyelocytic leukaemia (CNSAPL). After discovered the different tolarance between NB4 cell line and human cortex neuron to As2O3in vitro, and primarily cleared the safe range of As2O3 level in central nervous system (CNS), we created a non-invasive method to help As2O3 enter into CNS effectively. Methods Five volunteers with isolated meningle APL relapse received the new As2O3 regimen (mannitol helped As2O3 penetration) after accepted the conventional treatment: As2O3 0.16mg/kg/d diluted with 5%glucose 250ml common speed intravenous infusion with intensive intrathecal chemotherapy (MTX 12mg/dose + cytarabine 50mg / dose + Dexamethasone 10mg/dose) and showed chemotherapy resistance. The new regimen included 125ml of 20% mannitol bolus through medial cubital vein with the speed of 12„d`30ml / min, followed by As2O3 0.08mg/kg/d diluted with 250ml-20% mannitol intravenous infusion with the speed of 6ml /min, and then followed by As2O3 0.08mg/kg/d diluted with 5%glucose 250ml intravenous infusion with the speed of 0.5ml/min, meanwhile, associated with intensive intrathecal chemotherapy. The elemental arsenic levels in CSF and plasma during the new regimen performance were dynamic monitored with atomic fluorescence, and the differentiation and apoptosis of the blast cells in CSF were detected with flow cytometry assay. Results The elemental arsenic level in the CSF treated with mannitol helped As2O3 penetration was fluctuated between 0.04 mg /L (0.2 micromol /L) and 0.05mg / L(0.25 micromol /L), which was much higher than that with common speed As2O3 intravenous infusion, and reached to the As2O3 effectively therapeutic level. The blast cells in CSF showed significant differentiation and apoptosis after treated with mannitol helped As2O3 penetration. Three of the five patients obtained complete remission, two of them reached partial remission. Conclusions The new regimen of mannitol helped As2O3 penetration promoted the entrance of elemental arsenic to CNS, which might be benefit to prevent and cure CNS APL, especially to chemotherapy resistant CNS APL.

Determinants of cerebrospinal fluid arsenic concentration in patients with acute promyelocytic leukemia on oral arsenic trioxide therapy

The extent of and factors controlling arsenic penetration into the central nervous system (CNS) remain unclear. Elemental arsenic levels in 67 paired cerebrospinal fluid (CSF) and plasma samples from 9 patients with acute promyelocytic leukemia (APL) on oral arsenic trioxide (As2O3), obtained during intrathecal chemotherapy (treatment of CNS APL, n = 6; prophylaxis, n = 3) were measured. Median arsenic levels of CSF and plasma were 95.8 nmol/L (range, 3.5-318.9 nmol/L) and 498.9 nmol/L (range, 36.3-1892.8 nmol/L). As a group, CSF and plasma arsenic was linearly correlated (P < .001), with CSF at 17.7% the plasma level. The CSF/plasma arsenic ratio, which reflected the arsenic CSF penetration efficiency, varied significantly in individual patients (P < .001). Repeated intrathecal chemotherapy and presence of blasts in CSF did not affect the CSF/plasma arsenic ratio. Plasma arsenic was the only significant determinant of CSF arsenic levels. CSF arsenic was present at therapeutically meaningful levels, implying that As2O3 therapy might be beneficial in CNS APL.