Electrical and XPS studies of 100 MeV Si ion irradiated Pd/n-GaAs devices

The effect of Swift Heavy Ion (100 MeV Si⁷⁺) irradiation on electronic-transport of Pd/n-GaAs devices has been studied by I–V and C–V techniques. The chemical compositions of the interface have been studied by XPS/EDAX techniques. It is observed that the irradiated devices show a reduction in current and capacitance by few orders of magnitude. The C–V characteristics show a change in conductivity type from n- to p-type after the irradiation. On hydrogenation, the irradiated devices show a capacitance peak in C–V characteristics, which has been ascribed to As vacancies. The XPS studies of these devices, for various etching durations, show that the ratio of As:Ga has reduced after the irradiation, which indicates the formation of irradiation-induced As vacancies. This reduction in As:Ga ratio is also confirmed by EDAX measurement. The observed conductivity type change from n- to p-type (on the irradiation) seems to be due to the change of substitutional sites of dopant silicon atoms from Ga to As sites due to the irradiation-induced As vacancies.     

Gallium-induced Barbier coupling of carbonyl compounds with allyl iodide

Gallium metal readily prompted the allylation of aldehydes and ketones with allyl iodide. α, β-Unsaturated carbonyl compounds underwent only 1,2-addition.     

STM/nc-AFM investigation of (n×6) reconstructed GaAs(0 0 1) surface

We have investigated the n×6 reconstructed GaAs(0 0 1) surface with scanning tunneling and non-contact atomic force microscopy techniques (STM/nc-AFM). For the first time atomically resolved nc-AFM images of that surface are shown. The images confirm the presence of rows of arsenic dimers in the topmost layer as predicted by the current model of n×6 reconstructed surface. However, in contrast to previous reports we found that postulated As dimer sites are not fully occupied. Moreover, the images suggest that ×6 symmetry is present on the surface even in absence of the dimers. We show that due to probing of different surface properties nc-AFM and STM are complementary tools for complex surfaces investigation.     

Gallium-containing sulfide binary and ternary materials by atomic layer deposition: precursor reactivities and growth fine chemistries

Gallium sulfide (Ga_xS) and copper gallium sulfide (Cu_xGa_yS_z) were synthetized by atomic layer deposition (ALD), using copper acetylacetonate Cu(acac)₂, hexakis(dimethylamino)digallium [Ga(NMe₂)₃]₂ and hydrogen sulfide (H₂S). Thanks to the compatibility of the Cu_xS and Ga_xS ALD windows, a supercycle strategy that combines single growth cycles of the two binary compounds was used to generate the ternary material. A wide range of compositions and properties can be obtained from Ga-rich to Cu-rich via copper gallium sulfide thin films. Structural, morphological, and optoelectronic characterizations were performed on all films. Surface and in-depth chemical compositions were determined by X-ray photoelectron spectroscopy profiling, allowing a better understanding of the chemical reactions involved during the growth process. In the case of Ga_xS films, other Ga precursors have been tested. Our experimental observations, combined with reported ones and density functional theory calculation results have highlighted the specific reactivity of alkylamido precursor in ALD chemistry. Compositional studies revealed a significant O content which origin is discussed and represents an important challenge to address in ALD of sulfide materials in general.     

Syntheses and Crystal Structures of Di‐ and Trimercury Chlorogallates

Mercury(I) chloride reacts with gallium(III) chloride in benzene/1, 2‐dichlorobenzene solution to give the binuclear compound Hg₂(GaCl₄)₂ ( 1 ). Reduction of mercury(I) chloride with mercury in gallium(III) chloride‐benzene mixture leads to the trinuclear compound Hg₃(GaCl₄)₂ ( 2 ). The crystal structures of 1 and 2 were determined by single‐crystal X‐ray diffraction {Hg₂(GaCl₄)₂: triclinic, P1¯, a = 645.21(3), b = 654.44(3), c = 927.17(7) pm, α = 83.526(2)°, β = 74.915(2)°, γ = 61.863(3)°; Hg₃(GaCl₄)₂: monoclinic, P2₁/c, a = 715.79(1), b = 1501.59(4), c = 1421.43(4) pm, β = 98.9798(9)°}.