VACANCY-MEDIATED ATOMIC TRANSPORT IN NANO-CRYSTALS

International audienceAtomic transport in nano-crystals is still poorly studied experimentally. However, the knowledge of atomic transport kinetic and of the mechanisms allowing atoms to move in a volume exhibiting nano-scale dimensions (< 100 nm) is important for i) improving our fundamental knowledge concerning point defects' formation and migration energies, and atom-point defect interactions in nano-structures, as well as for ii) predicting mass transport in nano-structures, allowing the design of nano-structure fabrication processes to be developed at lower cost. In this article, atom probe tomography measurements were used to investigate the Ge distribution in 40 nm-wide Si nano-crystals in which the Ge flux was found to be ten times faster than in the bulk of a Si mono-crystal. The Ge atoms were found to be randomly distributed in the nano-crystals. No extended defect was found being able to explain an increase of Ge transport kinetic in the nano-crystals. Consequently, a scenario based on a higher equilibrium vacancy concentration at the nano-crystal surface (or interface) is proposed in order to explain the faster atomic kinetic measured in Si nano-crystals

Te homogeneous precipitation in Ge dislocation loop vicinity

International audienceHigh resolution microscopies were used to study the interactions of Te atoms with Ge dislocation loops, after a standard n-type doping process in Ge. Te atoms neither segregate nor precipitate on dislocation loops, but form Te-Ge clusters at the same depth as dislocation loops, in contradiction with usual dopant behavior and thermodynamic expectations. Atomistic kinetic Monte Carlo simulations show that Te atoms are repulsed from dislocation loops due to elastic interactions, promoting homogeneous Te-Ge nucleation between dislocation loops. This phenomenon is enhanced by coulombic interactions between activated Te2þ or Te1þ ions

VACANCY-MEDIATED ATOMIC TRANSPORT IN NANO-CRYSTALS

International audienceAtomic transport in nano-crystals is still poorly studied experimentally. However, the knowledge of atomic transport kinetic and of the mechanisms allowing atoms to move in a volume exhibiting nano-scale dimensions (< 100 nm) is important for i) improving our fundamental knowledge concerning point defects' formation and migration energies, and atom-point defect interactions in nano-structures, as well as for ii) predicting mass transport in nano-structures, allowing the design of nano-structure fabrication processes to be developed at lower cost. In this article, atom probe tomography measurements were used to investigate the Ge distribution in 40 nm-wide Si nano-crystals in which the Ge flux was found to be ten times faster than in the bulk of a Si mono-crystal. The Ge atoms were found to be randomly distributed in the nano-crystals. No extended defect was found being able to explain an increase of Ge transport kinetic in the nano-crystals. Consequently, a scenario based on a higher equilibrium vacancy concentration at the nano-crystal surface (or interface) is proposed in order to explain the faster atomic kinetic measured in Si nano-crystals

VACANCY-MEDIATED ATOMIC TRANSPORT IN NANO-CRYSTALS

International audienceAtomic transport in nano-crystals is still poorly studied experimentally. However, the knowledge of atomic transport kinetic and of the mechanisms allowing atoms to move in a volume exhibiting nano-scale dimensions (< 100 nm) is important for i) improving our fundamental knowledge concerning point defects' formation and migration energies, and atom-point defect interactions in nano-structures, as well as for ii) predicting mass transport in nano-structures, allowing the design of nano-structure fabrication processes to be developed at lower cost. In this article, atom probe tomography measurements were used to investigate the Ge distribution in 40 nm-wide Si nano-crystals in which the Ge flux was found to be ten times faster than in the bulk of a Si mono-crystal. The Ge atoms were found to be randomly distributed in the nano-crystals. No extended defect was found being able to explain an increase of Ge transport kinetic in the nano-crystals. Consequently, a scenario based on a higher equilibrium vacancy concentration at the nano-crystal surface (or interface) is proposed in order to explain the faster atomic kinetic measured in Si nano-crystals

Te homogeneous precipitation in Ge dislocation loop vicinity

International audienceHigh resolution microscopies were used to study the interactions of Te atoms with Ge dislocation loops, after a standard n-type doping process in Ge. Te atoms neither segregate nor precipitate on dislocation loops, but form Te-Ge clusters at the same depth as dislocation loops, in contradiction with usual dopant behavior and thermodynamic expectations. Atomistic kinetic Monte Carlo simulations show that Te atoms are repulsed from dislocation loops due to elastic interactions, promoting homogeneous Te-Ge nucleation between dislocation loops. This phenomenon is enhanced by coulombic interactions between activated Te2þ or Te1þ ions

First stages of Pd/Ge reaction: Mixing effects and dominant diffusing species

International audienceThe structure and the chemical composition of Pd germanides formed on Ge(100) were investigated using transmission electron microscopy (TEM), in-situ X-ray diffraction (XRD), and atom probe tomography (APT). An ultra thin Si film used as a marker was deposited on Ge(100) prior to Pd film deposition in order to identify the diffusing species during the Pd2Ge growth. The observations evidenced the formation of a thin interfacial poly-crystalline Pd2Ge layer during Pd room-temperature deposition on Ge(100). In-situ XRD thermal treatments ranging from 50 to 400 degrees C revealed that the Si marker had no influence on the sequential formation of Pd2Ge and PdGe. Ex situ APT and TEM characterizations showed that the Si marker layer was located closer to the Pd2Ge/Ge interface than to the Pd2Ge surface, after reaction. This result indicates that Ge and Pd self-diffusion are in the same order of magnitude during Pd2Ge growth. (C) 2016 Elsevier B.V. All rights reserved

Pdge Contact Fabrication On Ga-Doped Ge: Influence Of Implantation-Mediated Defects

PdGe contact fabrication on Ge(001) wafers doped with Ga is investigated using conventional complementary metal-oxide-semiconductor processes. Despite a p-type doping level of ~1.4 × 1020 cm−3, the resistivity of the PdGe contact is found to be twice higher than that of undoped Ge. Ga doping has no influence on the Pd reaction with Ge. However, the doping process and the Salicide process led to the formation of Ga-Pd defects in both sides of the PdGe/Ge interface, resulting from Ga and Pd co-segregation on Ge dislocation loops

Te Implantation In Ge(001) For N-Type Doping Applications

5×1015 Te+ ions cm-2 were implanted in an Ge(001) substrate using an industrial implanter with a Te+ beam energy of 180 keV. In addition to usual implantation-mediated defects observed in Ge with usual dopants, Te implantations lead to the formation of amorphous surface GeO clusters exhibiting micrometer scale sizes, as well as deep extended defects. Implantation defects promote the formation of two distributions of dislocation loops and clusters located at two different depths in the Ge substrate during annealing. No interactions between Te atoms and dislocation loops were observed. However, the formation of non-equilibrium Te-Ge clusters, probably mediated by Ge self-interstitials, was found to prevent the Te solubility to exceed ∼ 5 × 1019 cm-3 in Ge. The regular implantation method is shown to be ineffective for the production of high level n-type Ge doping using Te, due to the important Ge damage caused by Te implantation

Origin of the first-phase selection during thin film reactive diffusion: Experimental and theoretical insights into the Pd-Ge system

International audiencePd-Ge reactive-diffusion in two different samples Pd/Ge(001) and Pd/PdGe/Ge(001) was studied experimentally and theoretically, in order to clearly identify the driving force controlling the first-phase selection in the sequential phase formation regime. The experimental and theoretical results both show that only the atomic transport kinetic in the phases controls the first -phase selection: the phase exhibiting the fastest atomic self-diffusion forms first, even if its formation energy is not the lowest. (C) 2016 Elsevier Ltd. All rights reserved

Pdge Contact Fabrication On Se-Doped Ge

PdGe contact fabrication on Se-doped Ge(001) is investigated. PdGe thin film resistivity is two times lower if the PdGe layer is grown by Pd reactive diffusion on Se-doped Ge, compared to PdGe layer grown in the same condition on Se-free Ge. The phase sequence and the phase growth kinetics during Pd reactive diffusion with Ge are not modified by the presence of Se atoms. However, the PdGe film texture is different with Se, and Se segregates at the PdGe/Ge interface. These results suggest that Se atoms may be used to produce efficient contacts on n-type Ge