Ion Beam Implantation Research Articles

Optimization of L(+)-Lactic Acid Fermentation Without Neutralisation of Rhizopus Oryzae Mutant RK02 by Low-Energy Ion Implantation

In order to get an industrial strain which can yield a high concentration of lactic acid for ISPR (in situ product removal), the original strain Rhizopus oryzae RE3303 was mutated by low-energy ion beam implantation. A mutant RK02 was screened, and the factors such as the substrate concentration, nitrogen source concentration, inoculum size, seed age, aeration and temperature that affect the production of lactic acid were studied in detail. Under optimal conditions, the maximum concentration of L(+)-lactic acid reached 34.85 g/L after 30 h shake-flask cultivation without adding any neutralisation (5% Glucose added), which was a 146% increase in lactic acid production after ion implantation compared with the original strain. It was also shown that RK02 can be used in ISPR to reduce the number of times of separation.

Rf-driven ion sources for industrial applications (invited) (abstract)

The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory have been developing rf-driven ion sources for the last two decades. These sources are being used to generate both positive and negative ion beams. Some of these sources are operating in particle accelerators such as the Spallation Neutron Source (SNS) at Oak Ridge, while others are being employed in various industrial ion beam systems. There are four areas where the rf-driven ion sources are commonly used in industry. (1) In semiconductor manufacturing, rf-driven sources have found important applications in plasma etching, ion beam implantation, and ion beam lithography. (2) In material analysis and surface modification, miniature rf-ion sources can be found in focused ion beam systems. They can provide ion beams of essentially any element in the Periodic Table. The newly developed combined rf ion-electron beam unit improves greatly the performance of the secondary ion mass spectrometry tool. (3) For neutron production, rf ion source is a major component of compact, high flux D-D, D-T, or T-T neutron generators. These neutron sources are now being employed in boron neutron capture therapy (BNCT) as well as in neutron imaging and material interrogation. (4) Large area rf-driven ion source will be used in an industrial design neutral beam diagnostic system for probing fusion plasmas. Such sources can be easily scaled to provide large ion beam current for future fusion reactor applications.

A novel approach to microbial breeding—low-energy ion implantation

Low-energy ions exist widely in the natural world. People had neglected the interaction between low-energy ions and material; it was even more out of the question to study the relation of low-energy ions and the complicated organism until the biological effects of low-energy ion implantation were discovered in 1989. Nowadays, the value of low-energy ion beam implantation, as a new breeding way, has drawn extensive attention of biologists and breeding experts. In this review, the understanding and utilization of microbial breeding by low-energy ion beam irradiation is summarized, including the characteristics of an ion beam bioengineering facility, present status of the technology of low-energy ions for microbial breeding, and new insights into microbial biotechnology.

Fabrication of Si microstructures using focused ion beam implantation and reactive ion etching

Localized Ga implantation by means of a focused ion beam and subsequent deep reactive ion etching is used to fabricate microstructures or nanostructures in Si. It is found that the area irradiated with the focused ion beam acts as an etch stop in reactive ion etching. The etch rate ratio between the unimplanted and Ga-implanted area increases to 2.56 with an increasing Ga ion dose up to 1.59 × 1016 ions cm−2. However, the etch rate ratio decreases with further increase in ion dose and the surface of the etched Si microstructures is concave due to the effect of ion sputtering during focused ion irradiation. This technique is promising for the fabrication of 3D nanostructures in Si.

Focused ion beam implantation of Ga in nanocrystalline diamond: Fluence-dependent retention and sputtering

Focused ion beam implantation of 30-keV Ga+ ions in nanocrystalline diamond films was investigated by secondary-ion mass spectrometry (SIMS), using Cs+ primary ions for sputtering. Nine different implantation fluences ranging from 1×1013 to 1×1017 Ga+-ions/cm2 were used, with implanted areas of 40×40μm2. The Ga concentration distributions of these implants were determined by SIMS depth profiling. Such 30-keV Ga implants were also simulated by a dynamic Monte–Carlo code that takes into account the gradual change of the near-surface composition due to the Ga incorporation. In both approaches, an essentially linear increase of the Ga peak concentrations with fluence is found up to ∼1×1016cm−2; for higher fluences, the Ga content approaches a saturation level which is reached at about 2×1017cm−2. The measured and simulated peak concentrations of the Ga distributions are in good agreement. The most probable range obtained from the experiments corresponds closely with the respective value from the simulations; the peak width determined by SIMS is somewhat broader, possibly caused by the roughness of the films.

Nanometer-scale control of single quantum dot nucleation through focused ion-beam implantation

In situ ${\mathrm{Ga}}^{+}$ focused ion-beam (FIB) implantation has been used to control the nucleation of individual Ge islands on the Si(001) surface at the nanometer scale. The patterning technique consists of three steps: (i) low dose implantation, (ii) post-implantation annealing, and (iii) ultrahigh vacuum deposition of Ge. Varying the conditions for the Ga implantation and the post-implantation anneal allows four types of surface features to be created, and features that present a particular nanotopography after annealing act as island nucleation centers. Furthermore, because of Ga surface segregation during post-implantation annealing, Ge islands formed on patterned substrates present different characteristics compared to conventional Ge islands grown on the unmodified Si(001) surface. We discuss the influence of growth parameters and pattern feature topography on island nucleation, and identify the ideal growth conditions that lead to the formation of one coherent island on each pattern feature and the tightest island size distribution. The patterning technique described here can presumably be applied to systems other than $\mathrm{Si}∕\mathrm{Ge}$ and to techniques other than FIB that allow the creation of suitable local nanotopography.

Area laser crystallized LTPS TFTs with implanted contacts for active matrix OLED displays

We have developed a four mask low temperature poly-Si (LTPS) TFT process for p- and n-channel devices. Our PECVD deposited amorphous silicon is recrystallized to polycrystalline silicon with single area excimer laser crystallization while formation of drain and source is carried out with self aligned ion beam implantation. We have investigated implantation parameters, suitability of various metallizations as well as laser activation and annealing procedures. To prove the potential capability of our devices, which are suitable for conventional and inverted OLEDs alike, we have produced several functional active matrix backplanes implementing different pixel circuits. Our active matrix backplane process has been customized to drive small molecules as well as polymers, regardless if top or bottom emitting.

Target-ion source unit ionization efficiency measurement by a method of stable ion beam implantation

At the IRIS facility a rather precise method of the target-ion source unit ionization efficiency measurement has been developed. The method exploits an off-line mass-separator for the implantation of the ion beams of selected stable isotopes into a tantalum foil placed inside a Faraday cup in the focal plane of the mass-separator. After the implantation of the required amount of the investigated species, tantalum foil has been inserted into the volume of the target-ion source unit prepared for the on-line utilization at the IRIS on-line separator. The first tests have ensured the ionization efficiency values (90±10)% for Rb and (85±10)% for Cs in the empty combined target-ion source unit, which was used as a reference one. For the target-ion source unit with UC target material inside the measured value of the ionization efficiency of Rb was (52±20)%.

Magnetic Properties of Thin Metal-Polymer Films Prepared by High-Dose Ion-Beam Implantation of Iron and Cobalt Ions into Polyethylene Terephthalate

Thin metal-polymer composite films have been prepared by high-dose ion-beam implantation of Fe+ and Co+ ions into polyethylene terephthalate. The implantation of 40 keV ions at room temperature with doses from 2 · 1016 to 4 · 1017 cm−2 have been performed, with the ion current density of 4 μA/cm2. The effects of implantation dose on the film morphology and crystal structure have been investigated via atomic force and magnetic force microscopy and X-ray diffraction. The magnetic properties of synthesized structures have been studied by ferromagnetic resonance and with a vibrating-sample magnetometer. It was established that the properties of ion-implanted samples strongly depend on both the implantation dose and the type of implanted ions. The implantation dose at which the magnetic phase is formed for iron-implanted samples is significantly lower than that for cobalt-implanted ones. At high implantation doses due to polymer sputtering metal-containing layers are formed close to the sample surface for both ions. In this dose range the magnetic properties of implanted samples changed dramatically due to particle oxidation. The coercivity of synthesized layers reaches 180 and 300 Oe for iron- and cobalt-implanted samples, respectively.

Optical tomographic reconstruction of ion beam induced refractive index changes in silica

Refractive index changes induced by ion beam implantation can be used to produce photonic devices such as waveguides. Here, we relate the measured three-dimensional changes in refractive index produced by ion beam implantation to modeling of the implantation process. We use a quantitative phase microscopic method in conjunction with a tomographic reconstruction process to determine the change in the refractive index distribution within a silica optical fiber that has been selectively implanted with 2.4MeV H+ ions. The index profile is compared with numerical simulations of the ion vacancy and ionization using the stopping range of ions in matter program.

Improvement of astaxanthin production by a newly isolated Phaffia rhodozyma mutant with low-energy ion beam implantation

Isolation, characterization and identification of Phaffia sp. ZJB 00010, and improvement of astaxanthin production with low-energy ion beam implantation. A strain of ZJB 00010, capable of producing astaxanthin, was isolated and identified as Phaffia rhodozyma, based on its physiological and biochemical characteristics as well as its internal transcribed spacer (ITS) rDNA gene sequence analysis. With low-energy ion beam implantation, this wild-type strain was bred for improving the yield of astaxanthin. After ion beam implantation, the best mutant, E5042, was obtained. The production of astaxanthin in E5042 was 2512 microg g(-1) (dry cell weight, DCW), while the wild-type strain was about 1114 microg g(-1) (DCW), an increase of 125.5%. Moreover, the fermentation conditions of mutant E5042 for producing astaxanthin were optimized. The astaxanthin production under the optimized conditions was upscaled and studied in a 50-l fermentor. A genetically stable mutant strain with high yield of astaxanthin was obtained using low-energy ion beam implantation. This mutant may be a suitable candidate for the industrial-scale production of astaxanthin. Astaxanthin production in Phaffia rhodozyma could be efficiently improved by low-energy ion beam implantation, which is a new technology in the mutant breeding of micro-organisms. The mutant obtained in this work could potentially be utilized in industrial production of astaxanthin.

Optimization of L(+)-Lactic Acid Production from Xylose with Rhizopus Oryzae MutantRLC41-6 Breeding by Low-Energy Ion Implantation

In order to obtain an industrial strain with a higher L(+)-lacticacid yield, the strain Rhizopus oryzae PW352 was mutated by means ofnitrogen ion beam implantation and the mutant strain Rhizopus oryzaeRLC41-6 was obtained. An experimental finding was made in surprisethat Rhizopus oryzae mutant RLC41-6 is not only an L(+)-lactic acidproducer from corn starch but also an efficient producer ofL(+)-lactic acid from xylose. Under optimal conditions, theproduction of L(+)-lactic acid from 100 g/L xylose reached77.39 g/L after 144 h fed-batch fermentation. A high mutationrate and a wide mutation spectrum of low-energy ion implantationwere observed in the experiment.

Mutation of rice (Oryza sativa L.) LOX-1/2 near-isogenic lines with ion beam implantation and study of their storability

In this paper, Wanjian 2090 without LOX-1 and LOX-2, a rice variety, was irradiated by ion beam to screen LOX-1/2 near-isogenic lines, which had the similar genetic background while the enzyme activities of either LOX-1 or LOX-2 were different. When these rice seeds were stored under both the accelerated ageing conditions for 12 days and the natural ageing conditions for 18 months, our results showed that the germination percentages of lines lacking both LOX-1 and LOX-2 were always higher than those either with LOX-1 or with LOX-2. In addition, rice lines with the presence of both LOX-1 and LOX-2 have the lowest germination percentages. The germination percentages of all genotype near-isogenic lines under two ageing conditions were correlated positively and significantly.

Site-selective growth of self-assembled InAs quantum dots on focused ion beam patterned GaAs

A site-selective growth of self-organized InAs quantum dots (QDs) employing a combination of in-situ focused ion beam (FIB) implantation and self-organized molecular beam epitaxy (MBE) growth has been successfully demonstrated. First, a buffer layer of GaAs was grown by MBE before a square lattice of shallow holes with a pitch of 1–2 μm was fabricated by FIB implantation of Ga and In ions. Before InAs deposition, different procedures to remove the implantation damage were tested. The best results were obtained after re-evaporation of 3–5 nm GaAs. Another critical parameter that was carefully optimized is the deposited InAs amount. For the optimized process it was possible to induce growth of single QD in the hole with more than 50% probability. Between the shallow holes of 2 nm depths, no QD growth was observed. The optical quality of positioned dots was investigated by photoluminescence spectroscopy, employing a separate sample where the QDs were overgrown by GaAs cap layer. Excited-state interband transitions up to n=5 were observed from positioned QDs.

Focused ion beam implantation induced site-selective growth of InAs quantum dots

The site-selective growth of InAs quantum dots (QDs) by a combined focused ion beam (FIB) and molecular beam epitaxy (MBE) process has been demonstrated. An array of FIB modified spots on MBE grown GaAs was fabricated. Thereafter, an in situ annealing step followed by InAs deposition was performed. The InAs QDs were preferentially formed in the holes generated by the FIB. The influences of ion dose, annealing parameters, and InAs amount were investigated. With optimized parameters, the authors observe more than 50% single dot occupancy per holes. Photoluminescence spectra confirm the good optical quality of the QDs.

Mutagenic Effects of BM302:GO112 Induced by Low-Energy Ion Beam Implantation

Mutant strains of GO112 and BM302 with a high 2-keto-L-gulonic acid(2KLG) transformation rate induced by ion beam implantation wereseparately and combinatorially compared with the original strainsGO29 and BM80 to study the mutagenic effects of ion beamimplantation. Both the sole GO112 and mixed BM302:GO112 demonstratedimproved SNDH activity and 2KLG yield compared to the originalstrains. The mutant combinations of BM302:GO112 showed a longerstationary phase and higher biomass than BM80:GO29. The mutant BM302exhibited a stronger capacity to maintain a stable pH environment atmixed fermentation with Gluconobacter oxydans (G. oxydans) for 2KLGtransformation and facilitated the growth of G. oxydans comparedwith the original strain BM80. The promotive capacity to L-sorbosonedehydrogenase (L-SNDH) from the supernate of BM302 was 1.6-foldhigher than that of BM80. Genes encoded SNDH in GO29 and GO112 wereamplified and sequenced, and mutations including three transitions(CG → TA, CG → TA, GC → AT) andone transversion (AT → TA) were confirmed from GO29 toGO112. The corresponding amino acid was changed as Leu →Phe, Arg → Gln and Asn → Lys.

Bioeffects of Low Energy Ion Beam Implantation: DNA Damage, Mutation and Gene Transter

Low-energy ion beam implantation (10 ∼ 200 keV) has beenproved to have a wide range of biological effects and is broadlyused in the breeding of crops and micro-organisms.To understand itsmechanisms better and facilitate its applications, the developmentsin the bioeffects of low energy ion beam implantation in the pasttwenty years are summarized in this paper.

Electrostatic electron piston pump with in‐plane gate transistors

AbstractWe have demonstrated an electron pump with in‐plane gate (IPG) transistors fabricated by focused ion beam (FIB) implantation on GaAs–Alx Ga1–x As modulation‐doped heterostructure with a two‐dimensional electron gas (2DEG). The maskless fabrication process does not require any alignment between the circuit elements including the sources, the drains and the gates of the IPG transistors. Although, the device is operating at low frequencies (tens of kHz), it is capable to produce a current more than one order of magnitude higher than other electron pumps based on Coulomb blockade and single electron tunneling effects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dropwise condensation heat transfer on ion implanted aluminum surfaces

Stable dropwise condensation (DWC) of saturated steam has been achieved on an aluminum alloy Al 6951 disc with an average surface finish of about 0.15 μm by means of ion beam implantation technology with an ion dose of 10 16 N + cm −2 and an implantation energy of 20 keV. Measurements of the condensation heat transfer coefficient at steam pressures of 1200 and 1400 mbar were carried out as a function of surface subcooling on vertical plates of the same material which is commonly used for heat transfer equipment. Probably due to alloy inhomogeneities, only on about 50% of the plate surface DWC could be achieved, resulting in a maximum enhancement factor of 2.0 for DWC in comparison with theoretical values calculated by a corrected form of the Nusselt film theory. The heat transfer coefficient increases with increasing steam pressure and decreases with increasing surface subcooling. Furthermore, it was shown that condensation heat transfer cannot be enhanced if the ion implantation does not induce DWC. For the investigations, two different condensers have been used, one for the stability tests on discs and one for the heat transfer measurements on plates.

Impact of Ion Implantation on Licorice (Glycyrrhiza uralensis Fisch) Growth and Antioxidant Activity Under Drought Stress

Low energy ion beams are known to have stimulation effects on plantgeneration and to improve plants' intrinsic quality. In the presentstudy, the growth and physiological index of licorice implanted with0, 8, 10, 12 and 14× (2.6×1015) ions/cm2 wereinvestigated under well-watered and drought-stress conditions. Theresults showed that a proper dose of ion implantation wasparticularly efficient in stimulating the licorice growth andimproving the plant biomass significantly in both the well-wateredand drought-stress conditions. The physiological results of licoricemeasured by leaf water potential, lipid oxidation, soluble proteinand antioxidant system showed a significant correlation between ionimplantation and water regime except for leaf water potential.Therefore, the study indicated that ion implantation can enhancelicorice's drought tolerance by increasing the activity ofsuperoxide dismutase (SOD), catalase (CAT) and DPPH(1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability to loweroxidative damage to lipids in plants. Ion beam implantation,therefore, provides an alternative method to enhance licoricedrought tolerance.