MeV Si Ions Bombardment Research Articles

Surface morphology and topography evolution of soda-lime silica glass after 1.0 MeV Si ion bombardment

Surface pattern formation on soda-lime silica glass by 1 MeV Si ion irradiation impinging at an angle of 70° with respect to the surface normal has been studied. Modification of surfaces were analyzed for total ion fluences applied between up to ions/cm2. The surface morphology and topography were studied by scanning electron microscopy (SEM), and atomic force microscopy (AFM). These surface techniques enabled the determination of roughness, characteristic wavelengths, and correlation lengths. In addition, electron dispersive spectroscopy (EDS) scans were applied on the surface topography to study the variation of the Si content on the obtained surface patterns. From the measurement of these variables, linear and non-linear regimes were established. At linear regime, the surface morphology develops from an initial flat surface giving rise to ripples for fluences up to ions/cm2. As the ion bombardment continues surface evolve into wrinkles finalizing at cellular-like structures, growing under an anomalous scaling process. The EDS scans indicate the presence of shadowing effects. The morphological changes observed can be explained in terms of a combination of thermal mass diffusion and geometrical factors during ion irradiation, including shadowing and subsequent (secondary) surface erosion effects adapted to few MeV energies.

Thermoelectric and Optical Properties of Advanced Thermoelectric Devices from Different Multilayer Thin Films

Thermoelectric devices were prepared using different multilayered thin film structures in the order of Ge/Si+Ge, Si+Ge, Si, Sb+Ge, Ge and SiO2/SiO2+Ge by DC/RF Magnetron Sputtering. The thickness of the deposited thin films were measured using Filmetrics UV thickness measurement system. The prepared thermoelectric devices have been modified with 5 MeV Si ions bombardments at the different fluences (doses) using Pelletron high energy beam accelerator at Alabama A and M University to form quantum structures in the multilayer thin films to improve the efficiency of the thermoelectric devices. The conductivity measurements, the fluence dependence of the power factor measurements, the fluence dependence of thermal conductivity measurements and the figure of merit calculations of multilayered thin films at room temperature have been performed. After the thermoelectric devices were prepared, X-ray Diffraction, Scanning Electron Microscopy (SEM) + Energy-Dispersive X-beam Spectroscopy (EDS) and Scanning Transmission Electron Microscopy (TEM) measurements have been done from the cross section of the prepared multilayer thin films to give us some answer for the thickness of the fabricated thermoelectric devices.

Highly-Efficient Advanced Thermoelectric Devices from Different Multilayer Thin Films

The efficiency of the thermoelectric materials and devices is shown by the dimensionless Figure of merit, ZT. ZT is calculated by multiplying the Seebeck coefficient with square of the electrical conductivity and absolute temperature and dividing it all by the thermal conductivity. Thermoelectric devices were prepared using different multilayered thin film structures in the order of SiO2/SiO2 + Ge/Ge/Sb + Ge/Si/Si + Ge/Ge/Ge + Si by DC/RF Magnetron Sputtering. The prepared thermoelectric devices have been tailored with 5 MeV Si ions bombardment at the different fluences (doses) to form quantum structures in the multilayer thin films to improve the efficiency of the thermoelectric devices. Seebeck coefficients, van der Pauw-four probe resistivity, Hall Effect coefficient, density and mobility have been measured. After the samples were prepared, SEM/EDS data were collected. FIB/SEM images were provided to figure out the cross-section of the fabricated devices. Seebeck coefficients and electrical resistivity results were affected positively if the appropriate ion beam dose was selected.

Thermoelectric Generators from AgBiTe and AgSbTe Thin Films Modified by High-Energy Beam

The ternary chalcogenides AgBiTe2 and AgSbTe2 belong to the family of semiconductors with disordered NaCl cubic structure in which Ag and Sb occupy metal sublattices. Both compounds are very interesting due to their thermoelectric properties. We have grown single-layer AgBiTe and AgSbTe thin films on silicon (Si) and fused silica (Suprasil) substrates using electron beam deposition. High-energy (MeV) Si-ion bombardment was performed on the thin-film samples at five different fluences between 5 × 1013 ions/cm2 and 7 × 1015 ions/cm2. We have measured the thermoelectric efficiency (figure of merit, ZT) of the fabricated thermoelectric devices by measuring the cross-plane thermal conductivity using the third-harmonic (3ω) method, the cross-plane Seebeck coefficient, and the in-plane electrical conductivity using the van der Pauw method before and after MeV Si-ion bombardment. Rutherford backscattering spectrometry and the Rutherford Universal Manipulation Program (RUMP) simulation package were used to analyze the elemental composition and thickness of the deposited materials on the substrates. The RUMP simulation gave thicknesses for the AgBiTe and AgSbTe thin films of 270 nm and 188 nm, respectively. The figure of merit for AgBiTe started to decrease from the value of 0.37 for the virgin sample after bombardment. We saw similar decreasing behavior for the AgSbTe thin-film system. The figure of merit for AgSbTe started to decrease from the value of 0.88 for the virgin sample after bombardment. MeV Si-ion bombardment caused changes in the thermoelectric properties of the thin films.

Thermoelectric Figures of Merit of Zn4Sb3 and Zrnisn-based Half-heusler Compounds Influenced by Mev Ion-beam Bombardments

Semiconducting β-Zn4Sb3 and ZrNiSn-based half-Heusler compound thin films with applications as thermoelectric (TE) materials were prepared using ion beam assisted deposition (IBAD). High-purity solid zinc (Zn) and antimony (Sb) were evaporated by electron beam to grow the β-Zn4Sb3 thin film while high-purity zirconium (Zr) powder and nickel (Ni) tin (Sn) powders were evaporated by electron beam to grow the ZrNiSn-based half-Heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardment for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardment. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam couldcause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ω-method (3rd harmonic) measurement system to measure the cross-plane thermal conductivity, the van der Pauw measurement system to measure the electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.

MeV Si ion modifications on the thermoelectric generators from Si/Si + Ge superlattice nano-layered films

Abstract The performance of thermoelectric materials and devices is characterized by a dimensionless figure of merit, ZT = S 2 σT / K , where, S and σ denote, respectively, the Seebeck coefficient and electrical conductivity, T is the absolute temperature in Kelvin and K represents the thermal conductivity. The figure of merit may be improved by means of raising either S or σ or by lowering K . In our laboratory, we have fabricated and characterized the performance of a large variety of thermoelectric generators (TEG). Two TEG groups comprised of 50 and 100 alternating layers of Si/Si + Ge multi-nanolayered superlattice films have been fabricated and thoroughly characterized. Ion beam assisted deposition (IBAD) was utilized to assemble the alternating sandwiched layers, resulting in total thickness of 300 nm and 317 nm for 50 and 100 layer devices, respectively. Rutherford Backscattering Spectroscopy (RBS) was employed in order to monitor the precise quantity of Si and Ge utilized in the construction of specific multilayer thin films. The material layers were subsequently impregnated with quantum dots and/or quantum clusters, in order to concurrently reduce the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and raise the cross plane electrical conductivity. The quantum dots/clusters were implanted via the 5 MeV Si ion bombardment which was performed using a Pelletron high energy ion beam accelerator. We have achieved remarkable results for the thermoelectric and optical properties of the Si/Si + Ge multilayer thin film TEG systems. We have demonstrated that with optimal setting of the 5 MeV Si ion beam bombardment fluences, one can fabricate TEG systems with figures of merits substantially higher than the values previously reported.

Superlattice multinanolayered thin films of SiO2/SiO2 + Ge for thermoelectric device applications

Thermoelectric generators convert heat to electricity. Effective thermoelectric materials and devices have a low thermal conductivity and a high electrical conductivity. The performance of thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2 σT/ K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and K is the thermal conductivity. We have prepared 100 alternating layers of SiO2/SiO2+ Ge superlattice thin films using ion beam–assisted deposition for the thermoelectric generator device application. The 5 MeV Si ion bombardments were performed using the Center for Irradiation Materials’ Pelletron ion beam accelerator to form quantum dots and/or quantum clusters in the multinanolayer superlattice thin films to decrease the cross-plane thermal conductivity and increase the cross-plane Seebeck coefficient and cross-plane electrical conductivity. The thermoelectric and transport properties have been characterized for SiO2/SiO2+ Ge superlattice thin films.

Characterization of gold nanodots arrangements in SiO2/SiO2+Au nanostructured metamaterials

Effective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. For this study, we have prepared a thermoelectric generator device of SiO2/SiO2+Au multi-nano-layered thin film systems using ion beam-assisted deposition followed by 5 MeV Si ion bombardment. The ion bombardment causes the Au atoms to nucleate into metallic nanoclusters. However, as the kinetic energy of the Si ions decreases with the depth of the sample, so does the electronic stopping power responsible for the Au nucleation. This produces variations in the size and spacing of the nanoclusters. Here, we are investigating the effects of the size and arrangement variations within the device on the electrical and thermal transports within the system. We characterized the thin film system, using I–V characterization, conductance measurement, quasi-static capacitance, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy.

MeV Si ions bombardments effects on thermoelectric properties of SiO2/SiO2+Ge nanolayers

The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT=S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ, or decreasing K. We have prepared the thermoelectric generator device of SiO2/SiO2+Ge multilayer superlattice films using the ion beam assisted deposition (IBAD). The 5MeV Si ion bombardments have been performed using the AAMU Pelletron ion beam accelerator at five different fluences to make quantum structures (nanodots and/or nanoclusters) in the multilayer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after MeV Si ions bombardments at the different fluences we have measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity, Raman spectra to get some information about the sample structure and bond structures among the used elements in the superlattice thin film systems.

Effects of MeV Si ions bombardment on the thermoelectric generator from SiO 2/SiO 2 + Cu and SiO 2/SiO 2 + Au nanolayered multilayer films

The defects and disorder in the thin films caused by MeV ions bombardment and the grain boundaries of these nanoscale clusters increase phonon scattering and increase the chance of an inelastic interaction and phonon annihilation. We prepared the thermoelectric generator devices from 100 alternating layers of SiO 2/SiO 2 + Cu multi-nano layered superlattice films at the total thickness of 382 nm and 50 alternating layers of SiO 2/SiO 2 + Au multi-nano layered superlattice films at the total thickness of 147 nm using the physical vapor deposition (PVD). Rutherford Backscattering Spectrometry (RBS) and RUMP simulation have been used to determine the stoichiometry of the elements of SiO 2, Cu and Au in the multilayer films and the thickness of the grown multi-layer films. The 5 MeV Si ions bombardments have been performed using the AAMU-Center for Irradiation of Materials (CIM) Pelletron ion beam accelerator to make quantum (nano) dots and/or quantum (quantum) clusters in the multilayered superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after Si ion bombardments we have measured Seebeck coefficient, cross-plane electrical conductivity, and thermal conductivity in the cross-plane geometry for different fluences.

Thermoelectric Properties of SiO2/SiO2+CoSb3Multi Nanolayered Films Modified by Me v Si ions Bombardment

AbstractThe performance of the thermoelectric devices and materials is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ or decreasing K. We have prepared 100 alternating nanolayered films of SiO2/SiO2+CoSb3 using the ion beam assisted deposition (IBAD). The 5 MeV Si ions bombardments have been performed using the AAMU Pelletron ion beam accelerator to make quantum clusters in the nanolayered superlattice films at the three different fluences to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. We have characterized 100 alternating nanolayered films of SiO2/SiO2+CoSb3 before and after Si ion bombardments as we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for three different fluences.

Thermoelectric Properties of SiO2/SiO2+Ag Nanolayered Multilayer Films Effected by MeV Si Ions

AbstractWe have prepared 100 periodic nano-layers of SiO2/AgSiO2 with Au layer deposited on both sides as metal contacts. The deposited multi-layer films have a periodic structure consisting of alternating layers where each layer is 3.3 nm thick. The purpose of this research is to tailor the figure of merit of the thermoelectric materials generated from the nanolayers of nanocrystals of Ag with SiO2 as host and as buffer layer using a combination of co-deposition and MeV ions bombardment taking advantage of energy deposited in the MeV ion track to nucleate nanoclusters. The electrical and thermal properties of the nanolayered structures were studied before and after 5 MeV Si ions bombardment at various fluences to form nanocrystals. In addition to thermoelectric properties, some optical properties of the SiO2/SiO2+Ag multi-layer superlattice films have been studied.

MeV Si Ions Bombardment Effects on the Thermoelectric Properties of Si/Si+Ge Multi-Layer Superlttice Nanolayered Films

AbstractEffective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ or decreasing K. MeV ion bombardment caused defects and disorder in the film and the grain boundaries of these nano-scale clusters increase phonon scattering and increase the chance of an inelastic interaction and phonon annihilation. We have prepared 100 alternating layers of Si/Si+Ge nanolayered superlattice films using the ion beam assisted deposition (IBAD). The 5 MeV Si ions bombardments have been performed using the AAMU Pelletron ion beam accelerator to make quantum clusters in the nanolayered superlattice films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. We have characterized the thermoelectric thin films before and after Si ion bombardments as we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for different fluences

Effects of MeV Si Ions Modification on the Thermoelectric Properties of SiO2/SiO2+Cu Multilayer Thin Films

AbstractThe performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ, or decreasing K. We have prepared 100 alternating multi-nano layer of SiO2/SiO2+Cu superlattice films using the ion beam assisted deposition (IBAD). The 5 MeV Si ions bombardments have been performed at the different fluences using the AAMU Pelletron ion beam accelerator to make quantum clusters in the multi-layer superlattice thin films to decrease the cross plane thermal conductivity increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric thin films before and after Si ion bombardments we have measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for different fluences.

Effects of MeV Si ions bombardment on the thermoelectric properties of Zn 4Sb 3 and CeFe 2Co 2Sb 12 thin films

We deposited monolayer thin films of Zn 4Sb 3 and CeFe 2Co 2Sb 12 on 100 nm thick silicon dioxide coated Si substrates with 383 nm and 384 nm thickness respectively, using electron beam evaporation. Following the electron deposition, we performed post ion bombardment at a constant energy of 5 MeV while varying fluence from 10 12–10 15 ions/cm 2. The Si ions bombardment modified the electrical and phonon interactions in the material by causing the changes at the thermoelectric properties as well. We also report on the fluence dependence of the dimensionless figure of merit, ZT, Seebeck Coefficient, thermal conductivity and electrical conductivity. In addition, Rutherford backscattering spectrometry (RBS) was used to analyze the elemental composition and the thickness of the deposited material. The thickness of each film was also specified by interferometer measurements.

MeV Si ions bombardment effects on the thermoelectric properties of nano-layers of nanoclusters of Ag in SiO 2 host

We prepared 50 periodic nano-layers of SiO 2/Ag x SiO 2(1 − x) with Au layer deposited on both sides as metal contacts. The deposited multi-layer films have a periodic structure consisting of alternating layers where each layer is 10 nm thick. The purpose of this research is to generate nano-layers of nanocrystals of Ag with SiO 2 as host and as buffer layer using a combination of co-deposition and MeV ion bombardment taking advantage of energy deposited in the MeV ion track to nucleate nanoclusters. Our previous work showed that these nanoclusters have crystallinity similar to the bulk material. Nanocrystals of Ag in silica produce an optical absorption band at about 420 nm. Due to the interaction of nanocrystals between sequential nanolayers there is widening of the absorption band. The electrical and thermal properties of the layered structures were studied before and after 5 MeV Si ions bombardment at various fluences to form nanocrystals in layers of SiO 2 containing few percent of Ag. Rutherford Backscattering Spectrometry (RBS) was used to monitor the stoichiometry before and after MeV bombardments.

Surface modification of Si/Ge multi-layers by MeV Si ion bombardment

We made 50 periodic nano-layers of Si/Ge superlattice films with Au layers deposited on both sides as metal contacts. Each layer is 7.3 nm thick. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT. The purpose of this study is to improve the figure of merit of layered structures used as thermoelectric generators. The multi-layer Si/Ge films were then bombarded by 5 MeV Si ions at five different fluences to form nano-cluster structures. Rutherford Backscattering Spectrometry (RBS) was used to determine the total film thickness and stoichiometry. The total thickness was found as 364 nm. To get the figure of merit before and after MeV bombardments, we have measured the cross plane thermal conductivity by 3 ω (3rd harmonic) method, cross plane Seebeck coefficient and electrical conductivity using Van der Pauw method. The electronic energy deposited due to ionization by the MeV Si beam in its track produces nano-scale structures. Micro-Raman spectra of the multilayered Si/Ge thin films were acquired using a surface sensitive LabRam spectrophotometer, equipped with a He–Ne laser with μ = 632.18 nm excitation wavelength to show nanoscale structure production effect on quantum well confinement by MeV Si on bombardment.

MeV Si ions bombardment effects on the thermoelectric properties of Co0.1SbxGey thin films

We have grown three different monolayer Co0.1SbxGey (x=2,4,11 and y=15,7,15) thin films on silica substrates with varying thickness between 100 and 200nm using electron beam deposition. The high-energy (in the order of 5MeV) Si ion bombardments have been performed on samples with varying fluencies of 1×1012, 1×1013, 1×1014 and 1×1015ions/cm2. The thermopower, electrical and thermal conductivity measurements were carried out before and after the bombardment on samples to calculate the figure of merit, ZT. The Si ions bombardment caused changes on the thermoelectric properties of films. The fluence and temperature dependence of cross plane thermoelectric parameters were also reported. Rutherford backscattering spectrometry (RBS) was used to analyze the elemental composition of the deposited materials and to determine the layer thickness of each film.

MeV Si ion beam modification effects on the thermoelectric generator from Er0.1Fe1.9SbGe0.4 thin film

Effective thermoelectric materials and devices have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT. The purpose of this study is to improve the figure of merit of the single layer of Er0.1Fe1.9SbGe0.4 thin film used as thermoelectric generators. We have deposited the monolayer of Er0.1Fe1.9SbGe0.4 thin film on silicon and silica substrates with thickness of 302nm using ion beam assisted deposition (IBAD). Rutherford backscattering spectrometry (RBS) was used to determine the total film thickness and stoichiometry. The MeV Si ion bombardments were performed on single layer of Er0.1Fe1.9SbGe0.4 thin films at five different fluences between 5×1013−5×1015ions/cm2.The defect and disorder in the lattice caused by ion beam modification and the grain boundaries of these nanoscale clusters increase phonon scattering and increase the chance of annihilation of the phonon. The increase of the electron density of states in the miniband of the quantum dot structure formed by bombardment also increases the Seebeck coefficient and the electrical conductivity. We measured the thermoelectric efficiency of the fabricated device by measuring the cross plane thermal conductivity by the 3rd harmonic (3ω) method, the cross plane Seebeck coefficient, and the electrical conductivity using the Van Der Pauw method before and after the MeV ion bombardments.

Thermoelectric Generators of Sequentially Deposited Si/Si+Ge Nano-layered Superlattices

AbstractEffective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2sσ/ KTC, σ is the electrical conductivity T/KTC, where S is the Seebeck coefficient, T is the absolute temperature and KTC is the thermal conductivity. In this study we have prepared the thermoelectric generator device of Si/Si+Ge multi-layer superlattice films using the ion beam assisted deposition (IBAD). To determine the stoichiometry of the elements of Si and Ge in the grown multilayer films and the thickness of the grown multi-layer films Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package were used. The 5 MeV Si ion bombardments were performed to make quantum clusters in the multi-layer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity.Keywords: Ion bombardment, thermoelectric properties, multi-nanolayers, Figure of merit.