Direct Synthesis of Layer-Tunable and Transfer-Free Graphene on Device-Compatible Substrates Using Ion Implantation Toward Versatile Applications

Direct synthesis of layer-tunable and transfer-free graphene on technologically important substrates is highly valued for various electronics and device applications.State of the art in the field is currently a two-step process:a high-quality graphene layer synthesis on metal substrate through chemical vapor deposition(CVD)followed by delicate layer transfer onto device-relevant substrates.Here,we report a novel synthesis approach combining ion implantation for a precise graphene layer control and dual-metal smart Janus substrate for a diffusion-limiting graphene formation to directly synthesize large area,high quality,and layer-tunable graphene films on arbitrary substrates without the post-synthesis layer transfer process.Carbon(C)ion implantation was performed on Cu-Ni film deposited on a variety of device-relevant substrates.A well-controlled number of layers of graphene,primarily monolayer and bilayer,is precisely controlled by the equivalent fluence of the implanted C-atoms(1 monolayer~4×10^(15)C-atoms/cm^(2)).Upon thermal annealing to promote Cu-Ni alloying,the pre-implanted C-atoms in the Ni layer are pushed toward the Ni/substrate interface by the top Cu layer due to the poor C-solubility in Cu.As a result,the expelled C-atoms precipitate into a graphene structure at the interface facilitated by the Cu-like alloy catalysis.After removing the alloyed Cu-like surface layer,the layer-tunable graphene on the desired substrate is directly realized.The layer-selectivity,high quality,and uniformity of the graphene films are not only confirmed with detailed characterizations using a suite of surface analysis techniques but more importantly are successfully demonstrated by the excellent properties and performance of several devices directly fabricated from these graphene films.Molecular dynamics(MD)simulations using the reactive force field(ReaxFF)were performed to elucidate the graphene formation mechanisms in this novel synthesis approach.With the wide use of ion implantation technology in the microelectronics industry,this novel graphene synthesis approach with precise layer-tunability and transfer-free processing has the promise to advance efficient graphene-device manufacturing and expedite their versatile applications in many fields.

Molecular dynamics simulation study of nitrogen vacancy color centers prepared by carbon ion implantation into diamond

Nitrogen vacancy(NV)color centers in diamond have useful applications in quantum sensing andfluorescent marking.They can be gen-erated experimentally by ion implantation,femtosecond lasers,and chemical vapor deposition.However,there is a lack of studies of the yield of NV color centers at the atomic scale.In the molecular dynamics simulations described in this paper,NV color centers are pre-pared by ion implantation in diamond with pre-doped nitrogen and subsequent annealing.The differences between the yields of NV color centers produced by implantation of carbon(C)and nitrogen(N)ions,respectively,are investigated.It is found that C-ion implantation gives a greater yield of NV color centers and superior location accuracy.The effects of different pre-doping concentrations(400–1500 ppm)and implantation energies(1.0–3.0 keV)on the NV color center yield are analyzed,and it is shown that a pre-doping concentra-tion of 1000 ppm with 2 keV C-ion implantation can produce a 13%yield of NV color centers after 1600 K annealing for 7.4 ns.Finally,a brief comparison of the NV color center identification methods is presented,and it is found that the error rate of an analysis utiliz-ing the identify diamond structure coordination analysis method is reduced by about 7%compared with conventional identification+methods.

Structural Characterization of Carbon-implanted GaSb

Ion implantation induced damage in GaSb and its removal by rapid thermal annealing(RTA)have been investigated by Raman spectroscopy.The evolution of the Raman modes as a function of implantation fluence,annealing temperature and time has been analyzed.Results indicate that a lattice quality that is close to as-grown GaSb has been obtained by annealing the implanted samples at 500℃for 45 s.However,consequent surface analyses by scanning electron microscope(SEM)and atomic force microscope(AFM)show that a heavily perturbed layer contains voids due to the outdifiusion of Sb atoms on the surface remains.Mechanism of the damage recovery and the structure of the implanted layer are discussed based on the experimental results.

Biological Effects of Stevia rebaudianum Induced by Carbon Ion Implantation

The biological effects during seed germination were investigated after the dry seeds of Stevia rebaudianum Bertoni were implanted with carbon ion beam of 75 keV and 10 14 ions/cm 2. The results showed that the germination rate of carbon ion implanted seeds was slightly higher than that of the control, but the survival rate of the treated seedlings, on the contrary, was lower than that of the control (P<0.02), while the height of the treated seedlings was significantly higher than that of the control (P<0.01). On the 4th day after germination, the leaf cell wall in the treated group was thick, some high electron_dense substance deposited in the enlarged plasmodesma; Cell membrane creased with high electron_dense granules deposited on it. The plasma membrane protruded towards cell wall, and the granules shifted via plasmodesma or deposited onto cell wall. These phenomena may be related to the conveyance of implanted ions across cell wall, or be related to the accumulation of callose. In addition, the implantation of carbon ions could increase the lamellae of the chloroplast and cause high development of the chloroplast which sometimes contained two plastid centers in an individual chloroplast. Also, the highly developed cristae, abundant mitochondria and typical crystalloid structure in microbody could be found. All these results indicated that the anabolic and catabolic activities in the seedlings implanted with carbon ions before germination were obviously more active than those in the controls.

Effect of nitrogen ion implantation dose on torsional fretting wear behavior of titanium and its alloy

Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.

Numerical and Experimental Study of Localized Lifetime Control LIGBT by High Dose He Ion Implantation

A high speed LIGBT with localized lifetime control by using high dose and low en ergy helium implantation(LC-LIGBT) is proposed.Compared with conventional LIGB Ts,particle irradiation results show that trade-off relationship between turn- off time and forward voltage drop is improved.At the same time,the forward volta ge drop and turn-off time of such device are researched,when localized lifetime control region place near the p+-n junction,even in p+ anode.The results s how for the first time,helium ions,which stop in the p+ anode,also contribute to the forward voltage drop increasing and turn-off time reducing.

Screening of Biocontrol Strain Bacillus subtilis by N^+ Ion Beam Implantation

[Objective] This study was to investigate the effect of N＋ ion beam implantation on the survival rate and mutation rate of biocontrol strain Bacillus subtilis. [Method] The factors influencing B. subtilis ion beam implantation, including culture time, dilution concentration, solvent, drying time of mycoderm were optimized. B. subtilis cells were implanted by using ion beam at dose of 2.0×10^14～4.0×10^14 ions/cm2 and the energy of 30 kev. Then the methods of culturing colonies confronting each other on plate and Oxford cup diffusion were used to screening strains. [Result] The optimal parameters were found as follows： culture in liquid for 20-24 h, dilution with sterile water to 106 cells/ml and drying time of 60 min for sample preparation; the optimal N＋ ion beam implantation dose of 2.0×10^14～4.0×10^14 ions/cm2 at the energy of 30 kev, the survival rate of 8.43%-26.71% and the mutation rate of 3.50%-5.43%. [Conclusion] This study provided reference for ion beam implantation mutation of B. subtilis.

Investigation of 980nm Ridge Waveguide Lasers with Current Non-Injection Regions by He Ion Implantaion

The technology of He ion implantation for improving the catastrophic optical damage (COD) level of 980nm semiconductor lasers is introduced.After He ion implantation,p-GaAs obtain higher resistivity than before.About 25μm-long current non-injection regions are introduced near both facets,where the injection current is blocked by high resistivity area.The current non-injection regions can reduce carriers inject to facets,and the rate of the non-radiative recombination are reduced.So the COD level is higher than before.The He ion implantation LDs exhibit no COD failure until the rollover occure at a mean maximum power of 440.5mW.Mean COD level of conventional LDs is given as 407.5mW.Compared to conventional LDs,the mean maximum output power level of He ion implantation LDs is improved by 8%.

Theoretical Investigation of Pinch off Voltage of Box-Like Ion-Implanted 4H-SiC MESFETs

A precise theoretical calculation off the pinch of voltage of the box-like ion implantation 4H-SiC MESFETs is investigated with the consideration of the effects of the ion-implanted channel and the depth of MESFETs channel.The implant depth profile is simulated using the Monte Carlo simulator TRIM.The effects of parameters such as temperature,acceptor density,and activation rate on channel depth a,pinch off voltage are studied.

Fabrication of n^+ Polysilicon Ohmic Contacts with a Heterojunction Structure to n-Type 4H-Silicon Carbide

Polysilicon ohmic contacts to n-type 4H-SiC have been fabricated. TLM （transfer length method） test patterns with polysilicon structure are formed on n-wells created by phosphorus ion （P^＋） implantation into a Si-faced p-type 4H-SiC epilayer. The polysilicon is deposited using low-pressure chemical vapor deposition （LPCVD） and doped by phosphorous ions implantation followed by diffusion to obtain a sheet resistance of 22Ω/□. The specific contact resistance pc of n^＋ polysilicon contact to n-type 4H-SiC as low as 3.82 × 10^-5Ω· cm^2 is achieved. The result for sheet resistance Rsh of the phosphorous ion implanted layers in SiC is about 4.9kΩ/□. The mechanisms for n^＋ polysilicon ohmic contact to n-type SiC are discussed.

Monolithic Integration of a Widely Tunable Laser with SOA Using Quantum-Well Intermixing

This paper presents an SG-DBR with a monolithically integrated SOA fabricated using quantum-well intermixing （QWI） for the first time in China's Mainland. The wavelength tuning range covers 33nm and the output power reaches 10mW with an SOA current of 50mA. The device can work at available channels with SMSR over 35dB.

Two Steps B Ion-Implantation of Diamond Film Grown on an n-Type Si Substrate and Its p-n Junction Effects

Polycrystalline diamond thin films are deposited on an n-type Si substrates by hot filament chemical vapor deposition,and then are implanted with boron ions in a 200keV ion implanter.In order to achieve a better distribution of the implanted element,boron ions are implanted by two steps:implanting boron ions with the energy of 70keV first,and then with the energy of 100keV.The homogeneous distribution of the B ion is gained.The current-voltage characteristics of the samples are studied.It is found that the p-n heterojunction effect is achieved in these samples.

Properties of Y\|Silicides Synthesized Layer by Y Implantation and RTA Annealing\+*

Synthetic silicides with good properties were prepared,as Y ions were implanted into silicon using metal vapor vacuum arc (MEVVA) ion implantor and annealed by Rapid Thermal Annealing (RTA).The structure of synthetic silicides has been investigated with the analysis of channeled low angle emergence and TEM.Three layers could be observed in the implanted region as the implanting ion flux is selected as 25μA/cm\+2.The thickness of the silicide layer is about 60—80nm.The defect density N \-d and sheet resistance R \-s decrease with the increase of the ion flux.After RTA annealing of the implanted sample,the N\-d and R\-s decreased obviously.R\-s decreased from 54Ω/□ to 14Ω/□.The minimum of resistivity is 84μΩ·cm.It is evident that electrical properties of the Y silicides can be improved by RTA.The formation of the silicides with YSi and YSi\-2 are confirmed by X\|ray diffraction (XRD) analysis.With the analysis of low angle emergence,important information exposed from the depth profiles of atoms and lattice distortion in an implanted region would be used to study the synthesis of silicides.

Effects of Al and N plasma immersion ion implantation on surface microhardness,oxidation resistance and antibacterial characteristics of Cu

A1 and N were introduced into copper substrate using plasma immersion ion implantation （PIII） in order to enhance its hardness and oxidation resistance. The dosage of N ion is 5 × 1016 cm-2, and range of dosage of A1 ion is 5× 1016-2× 1017 cm-2. The oxidation tests indicate that the copper samples after undergoing PIII possess higher oxidation resistance. The degree of oxidation resistance is found to vary with implantation dosage of AI ion. The antibacterial tests also reveal that the plasma implanted copper specimens have excellent antibacterial resistance against Staphylococcus aureus, which are similar to pure copper.

Phenotype Observation and Variation Analysis of F_2 Generation of Ion Implanted Chili Pepper Seeds

[Objective]The aim was to investigate inheritance of the mutagenic properties caused by ion implantation from F1 to F2 generation in chili pepper.[Method]Chili pepper seeds were implanted with different ion combinations at different doses,and the F1 generation seeds of five groups in which biological mutation occurred were selected to sow in the field.Then the main phenotype changes in F2 generation were observed,the biochemical changes caused by ion implantation were analyzed by determination of peroxidase isozyme.[Result]Seed implanted with 9×1011 P2＋/cm2 and 1×1012 Cu2＋/cm2（No.21）on its both sides could maintain the superiority in yield per plant to F2 generation,while the mutagenic effects of F1 generation in other groups were not inherited by the F2 generation.[Conclusion]The prominent biological characters induced in the seeds of group No.21 were relatively inherited,so the seeds were worth further breeding.

Formation of Nickel Based Ohmic Contact to High Energy Vanadium Implanted n-Type 4H-SiC

The diffusion behavior of vanadium （V） implanted in SiC is investigated by secondary ion mass spec- trometry. Significant redistribution, especially out-diffusion of vanadium towards the sample surface, is not ob- served after 1650℃ annealing. Higher carrier concentration is obtained due to a lack of compensation of vanadium in the surface region. The electrical characteristics of Ni contacts to V-implanted n-type 4H-SiC are investigated using a linear transmission line method. A specific contact resistance as low as 4.4 × 10^-3Ω · cmA^2 is achieved after annealing at 1050℃ for 10min in gas ambient consisting of 90% N2 and 10% H2 X-ray diffraction analysis shows the formation of Ni2 Si and graphite phase at the interface after annealing. This provides the evidence that the car- bon vacancies,resulting from the out-diffusion of carbon atoms from SiC, contribute to the formation of ohmic contact through the reduction of effective Schottky barrier height for the transport of electrons.

Surface characteristics,corrosion behavior,and antibacterial property of Ag-implanted NiTi alloy

NiTi shape memory alloy was modified by Ag ion implantation with different incident doses to improve its antibacterial property. The atomic force microscopy, auger electron spectroscopy, and X-ray photoelectron spectroscopy show that the surface of NiTi alloy is covered by TiO2 nano-film with embedded pure Ag with a peak concentration of 5.0 at% at the incident dose of 1.5 x10^17 ions.cm-a, and Ni concentration is reduced in the super- ficial surface layer. The surface roughness reaches the maximum value nearly twice higher than the control sample at the incident dose of 1.5x10^17 ions.cm-2. The potentiodynamic anodic polarization curves show that the Ag-implanted NiTi samples possess higher self-corrosion potential （Ecorr） and lower self-corrosion current density （icor0 but lower breakdown potential （Ebr）. Therefore, the corrosion resistance of the Ag-NiTi is comparable to, if not better than, the untreated NiTi. The antibacterial tests reveal that there is a distinct reduction of the germ numbers on the Ag-NiTi, which is due to the direct contact between Ag and germ, and enhanced by the leaching Ag ions.

Effects of Si Ion Implantation on the Total-Dose Radiation Properties of SIMOX SOI Materials

To improve the total-dose radiation hardness,silicon-on-insulator （SOI） wafers fabricated by the separation-by-implanted-oxygen （SIMOX） method are modified by Si ion implantation into the buried oxide with a post anneal. The ID- VG characteristics can be tested with the pseudo-MOSFET method before and after radiation. The results show that a proper Si-ion-implantation method can enhance the total-dose radiation tolerance of the materials.

Antibacterial properties and corrosion resistance of AISI 420 stainless steels implanted by silver and copper ions

Silver or copper ions are often chosen as antibacterial agents. But a few reports are concerned with these two antibacterial agents for preparation of antibacterial stainless steel （SS）. The antibacterial properties and corrosion resistance of AISI 420 stainless steel implanted by silver and copper ions were investigated. Due to the cooperative antibacterial effect of silver and copper ions, the Ag/Cu implanted SS showed excellent antibacterial activities against both Gram-negative Escherichia coli （E. coli） and Gram-positive Staphylococcus aureus （S. aureus） at a total implantation dose of 2~ 1017 ions/cm2. Electrochemical polarization curves revealed that the corrosion resistance of Ag/Cu implanted SS was slightly enhanced as compared with that of un-implanted SS, The implanted layer was characterized by X-ray photoelec- tron spectroscopy （XPS）. Core level XPS spectra indicate that the implanted silver and copper ions exist in metallic state in the implanted layer.

ION HEATING PROCESS DURING PLASMA IMMERSION ION IMPLANTATION

The research on plasma immersion ion implantation has been conducted for a little over ten years. Much is needed to investigate including processing technlogy, plasma sheath dynamics, interaction of plasma and surface, etc. Of the processing methods elavated temperature technique is usually used in PIII to produce a thick modified layer by means of the thermal diffusion. Meanwhile plasma ion heating is more recently developed by Ronghua Wei et al[1]. Therefore the temeperature is a critical parameter in plasma ion processing. In this paper we present the theoretical model and analysize the effect of imlantation voltage, plasma density, ion mass,etc on the temperature rise.