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During cancer development, host’s tumorigenesis and immune signals are released to and informed by circulating molecules, like cell-free DNA (cfDNA) and RNA (cfRNA) in blood. However, these two kinds of molecules are still not systematically compared in gastrointestinal cancer. Here, we profiled 4 types of cell-free omics data from colorectal and stomach cancer patients, and assayed 15 types of genomic, epi-genomic, and transcriptomic variations. First, we demonstrated that the multi-omics data were more capable of detecting cancer genes than the single-omics data, where cfRNAs were more sensitive and informative than cfDNAs in terms of detection ratio, variation type, altered number, and enriched functional pathway. Moreover, we revealed several peripheral immune signatures that were suppressed in cancer patients and originated from specific circulating and tumor-microenvironment cells. Particularly, we defined a γδ-T-cell score and a cancer-associated-fibroblast (CAF) score using the cfRNA-seq data of 143 cancer patients. They were informative of clinical status like cancer stage, tumor size, and survival. In summary, our work reveals the cell-free multi-molecular landscape of colorectal and stomach cancer, and provides a potential monitoring utility in blood for the personalized cancer treatment.

The utility of cell-free nucleic acids in monitoring cancer has been recognized by both scientists and clinicians. In addition to human transcripts, a fraction of cell-free nucleic acids in human plasma were proven to be derived from microbes and reported to have relevance to cancer. To obtain a better understanding of plasma cell-free RNAs (cfRNAs) in cancer patients, we profiled cfRNAs in ~300 plasma samples of 5 cancer types (colorectal cancer, stomach cancer, liver cancer, lung cancer, and esophageal cancer) and healthy donors (HDs) with RNA-seq. Microbe-derived cfRNAs were consistently detected by different computational methods when potential contaminations were carefully filtered. Clinically relevant signals were identified from human and microbial reads, and enriched Kyoto Encyclopedia of Genes and Genomes pathways of downregulated human genes and higher prevalence torque teno viruses both suggest that a fraction of cancer patients were immunosuppressed. Our data support the diagnostic value of human and microbe-derived plasma cfRNAs for cancer detection, as an area under the ROC curve of approximately 0.9 for distinguishing cancer patients from HDs was achieved. Moreover, human and microbial cfRNAs both have cancer type specificity, and combining two types of features could distinguish tumors of five different primary locations with an average recall of 60.4%. Compared to using human features alone, adding microbial features improved the average recall by approximately 8%. In summary, this work provides evidence for the clinical relevance of human and microbe-derived plasma cfRNAs and their potential utilities in cancer detection as well as the determination of tumor sites.

Background: The utilities of cell free nucleic acids in monitoring cancer have been recognized by both scientists and clinicians. In addition to human transcripts, a fraction of cell free nucleic acids in human plasma were proved to derived from microbes, and reported to have some relevance to cancer. Methods: To get a better understanding of plasma cell free RNAs (cfRNAs) in cancer patients, we profiled cfRNAs in ~300 plasma samples of five cancer types (colorectal cancer, stomach cancer, liver cancer, lung cancer, esophageal cancer) and healthy donors with RNA-seq. Results: Microbe derived cfRNAs were consistently detected by different computational methods when potential contaminations were carefully filtered. Clinically relevant signals can be identified from human and microbial reads, and alteration in human cfRNA expression and virus abundance both suggests some cancer patients were immunosuppressed, as indicated by enriched KEGG pathways of downregulated human genes and higher prevalence torque teno virus. Our data supports the diagnostic value of human and microbe derived plasma cfRNAs for cancer detection, as an area under receiver operating characteristic (ROC) curve of 0.931 for distinguishing cancer patients from healthy donors was achieved on validation set, using both human and microbial features. Moreover, these cfRNAs both have some cancer type specificity, and could distinguish tumors of different primary locations. Compared to using human feature alone, combining human and microbial features improves the average validation accuracy of between cancer type classification by 11.5%. Conclusions: In summary, this work provides evidence for the clinical relevance of human and microbe derived plasma cfRNAs, and their potential utilities in cancer detection, and determination of tumor sites.

Rationale: Long extracellular RNAs (exRNAs) in plasma can be profiled by new sequencing technologies, even with low abundance. However, cancer-related exRNAs and their variations remain understudied. Methods: We investigated different variations (i.e. differential expression, alternative splicing, alternative polyadenylation, and differential editing) in diverse long exRNA species (e.g. long noncoding RNAs and circular RNAs) using 79 plasma exosomal RNA-seq (exoRNA-seq) datasets of multiple cancer types. We then integrated 53 exoRNA-seq datasets and 65 self-profiled cell-free RNA-seq (cfRNA-seq) datasets to identify recurrent variations in liver cancer patients. We further combined TCGA tissue RNA-seq datasets and validated biomarker candidates by RT-qPCR in an individual cohort of more than 100 plasma samples. Finally, we used machine learning models to identify a signature of 3 noncoding RNAs for the detection of liver cancer. Results: We found that different types of RNA variations identified from exoRNA-seq data were enriched in pathways related to tumorigenesis and metastasis, immune, and metabolism, suggesting that cancer signals can be detected from long exRNAs. Subsequently, we identified more than 100 recurrent variations in plasma from liver cancer patients by integrating exoRNA-seq and cfRNA-seq datasets. From these datasets, 5 significantly up-regulated long exRNAs were confirmed by TCGA data and validated by RT-qPCR in an independent cohort. When using machine learning models to combine two of these validated circular and structured RNAs (SNORD3B-1, circ-0080695) with a miRNA (miR-122) as a panel to classify liver cancer patients from healthy donors, the average AUROC of the cross-validation was 89.4%. The selected 3-RNA panel successfully detected 79.2% AFP-negative samples and 77.1% early-stage liver cancer samples in the testing and validation sets. Conclusions: Our study revealed that different types of RNA variations related to cancer can be detected in plasma and identified a 3-RNA detection panel for liver cancer, especially for AFP-negative and early-stage patients.

The effects of the processing conditions on the formation of buried oxide precipitates in He and O co-implanted Si were investigated by the combination of Fourier transform infrared (FTIR) absorption spectroscopy, depth-resolved positron annihilation Doppler spectroscopy, and transmission electron microscopy (TEM). Silicon wafers were implanted with 50 keV He ions at a fluence of 2 x 10(16) cm(-2) and subsequent 150 key O ions at a fluence of 2 x 10(17) cm(-2). For comparison, reference Si wafers were only implanted with 150 keV O ions. The Si-O-Si stretching frequency increases while the peak width of the Si-O-Si stretching absorption band decreases with an increase in annealing temperature. After the same annealing, the peak width of the Si-O-Si stretching absorption band in the He and O co-implanted sample is significantly larger than that in the reference sample. Two kinds of vacancy-type defects are observed by positrons, i.e., vacancy-type defects and vacancy-oxygen complexes. The characteristic S values of vacancy-type defects and vacancy-type complexes in the He and O co-implanted sample are smaller than those of the reference sample. In addition, the thickness of the buried oxide layer in the He and O co-implanted sample is smaller than that in the reference sample. After annealing at 1473 K, the O content is larger in the He and O co-implanted sample compared to that in the reference sample. (C) 2012 Elsevier Ltd. All rights reserved.

Epitaxial GaN layers grown by MOCVD on c-plane sapphire substrates were irradiated with 5.3 MeV Kr23+ and 2.3 MeV Ne8+ ions to various fluences. The pristine and the irradiated GaN samples were characterized using high resolution X-ray diffraction (HRXRD), UV-visible transmittance spectrum and Raman scattering spectrum analysis. The HRXRD results show an obvious increase in the FWHM and a decrease in the intensity of the GaN (0002) peak with increasing ion fluences. Meanwhile the UV-visible transmittance spectra show a decrease in the band gap value after irradiation. The Raman scattering spectrum shows that new Raman bands around 300 and 670 cm(-1) appear with increasing ion fluences. The new Raman bands can be ascribed to disorder-activated Raman scattering (DARS) from the highest acoustic-phonon branch and the optical-phonon branch at the brillouin zone boundaries, respectively. (C) 2013 Elsevier B.V. All rights reserved.

Polystyrene (PS) films were irradiated with 1.157 GeV Fe-56 ions at room temperature to fluences of 1 x 10(12) ions/cm(2) at various electronic energy loss values. Ultraviolet-visible (UV-vis) spectra were measured to investigate the optical properties of the irradiated materials. Optical constants of virgin and irradiated PS were evaluated in the UV-vis frequence range through fitting of UV-vis spectra with the multi-Lorentz model. Furthermore, effective medium theory was applied to evaluate the optical constants of materials in the ion track area. It is found that the refractive index of ion track material decreased significantly in the ultraviolet-visible range whereas its extinction coefficient increased. Gas atom release and carbon atom conglomerating are believed to be the reason. The extracted track radius and its variation with electronic energy loss values are in good agreement with earlier studies. (C) 2012 Elsevier B.V. All rights reserved.

Specimens of 6H–SiC were implanted with Xe ions with multiple kinetic energies at room temperature to obtain nearly uniform Xe concentrations of 7.5, 30, 150 at. ppm, respectively, and were subsequently thermally annealed under high vacuum. The lattice damage and nanohardness of specimens were studied with high resolution X-ray diffraction spectrometry and nanoindentation measurements. In the low dose specimen (7.5 at. ppm), the occurrence of a plateau (with sub-peaks) at low angle side of the SiC (0 0 0 1 2) peak suggests a strain gradient in the direction normal to the specimen surface. Upon subsequent thermal annealing the strain relaxes gradually. The relaxation activation energy of the strain was estimated with Arrhenius law. For the specimens implanted to 30 and 150 at. ppm Xe, the disappearance of the plateau or peak indicates that the implanted region has been amorphized. However, a satellite peak near the main peak reappears after the thermal annealing. In addition, the main peak broadens toward high angle side after the annealing as the result of a shrinkage of crystal lattice. The nanohardness value of the specimen implanted to 7.5 at. ppm exceeds that of virgin SiC, whereas it is opposite for the case of 30 and 150 at. ppm implantation due to the formation of amorphous regions. Changes of nanohardness with thermal annealing temperature were studied. Underlying mechanisms were discussed.

Thermally grown amorphous SiO2 (a-SiO2) films were implanted at room temperature (RT) with 100 keV C-ions to 5.0×1017 ions/cm2. These samples were irradiated at RT with 853 MeV Pb-ions to 1.0×1012 and 5.0×1012 ions/cm2. Then the samples were investigated using Transmission Electron Microscopy (TEM) at RT. Significant microstructure modifications were observed in C-doped a-SiO2/Si samples after high energy Pb-ion irradiations, and the formation of new structures depended strongly on the Pb-ion irradiation fluences. For example, tracks in high density were observed in a 1.0×1012 Pb/cm2 irradiated and C-doped sample. Additionally, the length of tracks grows, and a large number of 8H-SiC nanocrystals can be seen in the film when irradiation fluence is increased to 5.0×1012 Pb/cm2. Possible modification processes of C-doped a-SiO2 under swift heavy ion irradiations are briefly discussed.

Wurtzite GaN epilayers irradiated at room temperature with 308 MeV 129Xe35+ ions to fluences of 1 × 1013 and 3 × 1013 cm−2 have been studied by contact mode atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), micro-Raman scattering and photoluminescence (PL) spectroscopy. The AFM images showed that the surface of GaN films was etched efficiently due to the Xe ion irradiation. The initial step-terrace structure on GaN surface was eliminated completely at a fluence of 3 × 1013 cm−2. HRXRD and Raman results indicated that the Xe ion irradiation led to a homogenous lattice expansion throughout the entire ∼3 μm-thick GaN films. The lattice expansion as well as the biaxial compressive stress of the films was increasing with the increase of ion fluence. PL measurements showed that a dominant yellow luminescence band in the as-grown GaN films disappeared, but a blue and a green luminescence bands were produced after irradiation. Based on these results, the strong electronic excitation effect of 308 MeV Xe ions in GaN is discussed.

In(0.15)Ga(0.83)N/GaN bilayers irradiated with 2.3 MeV Ne and 5.3 MeV Kr ions at room temperature were studied by high-resolution X-ray diffraction (HRXRD) and micro-Raman scattering. The Ne ion fluences were in the range from 1 x 10(12) to 1 x 10(15) cm(-2), and the Kr ion fluences were in the range from 1 x 10(11) to 1 x 10(13) cm(-2). Results show that the structures of both In(0.15)Ga(0.85)N and GaN layers remained almost unchanged for increasing fluences up to 1 x 10(13) and 1 x 10(12) cm(-2) for Ne and Kr ion irradiations, respectively. After irradiation to higher fluences, the GaN layer was divided into several damaged layers with different extents of lattice expansion, while the In(0.15)Ga(0.83)N layer exhibited homogenous lattice expansion. The layered structure of GaN and the different responses to irradiation of the GaN and In(0.15)Ga(0.85)N layers are discussed. (C) 2011 Elsevier B.V. All rights reserved.

In the present work the erosion behavior on the surface of GaN epi-layer by the impact of various slow highly charged heavy ions (SHCIs, including Arq+. Xeq+ and Pbq+, in two incidence geometries) was investigated. Atomic force microscopy reveals a well-defined threshold of potential energy carried by the incident heavy ions accounting for the surface erosion. This threshold also depends on the projected range of the SHCIs, the longer the projected range, the higher the potential energy required for the onset of surface erosion. And the etched depth is close to a linear function of potential energy deposited, increasing with the potential energy increases. Moreover, the etching rate for 60 degrees off normal incidence is by more than a factor of 2 larger than etching rate for normal incidence, and the etch rate by Xeq+ is larger than by Pbq+ under the same potential energy and incident direction. And a mechanism is discussed. (C) 2010 Elsevier B.V. All rights reserved.

The structural stability of C60 films under the bombardment of 1.95 GeV Kr ions is investigated. The irradiated C60 films were analyzed by Fourier Transform Infrared (FTIR) spectroscopy and Raman scattering technique. The analytical results indicate that the irradiation induced a decrease of icosahedral symmetry of C60 molecule and damage of C60 films; different vibration modes of C60 molecule have different irradiation sensitivities; the mean efficient damage radius obtained from experimental data is about 1.47 nm, which is in good agreement with thermal spike model prediction.

Silica glass samples were implanted with 1.157 GeV (56)Fe and 1.755 GeV (136)Xe ions to fluences range from 1 x 10(11) to 3.8 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E' center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E' center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E' center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (alpha band), 3.2 eV (beta band) and 2.67 eV (gamma band) when excited at 5 eV. The intensities of alpha and gamma bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of beta band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of alpha and gamma bands and electronic energy loss processes determine the bleaching of beta band in heavy ion irradiated silica glass. (c) 2009 Elsevier B.V. All rights reserved.

In this paper, an investigation on the micro-structure of an Fe-base oxide-dispersion-strengthened (ODS) alloy irradiated with high-energy 20Ne ions to different doses at a temperature around 0.5Tm (Tm is the melting point of the alloy) is presented. Investigation with the transmission electron microscopy found that the accelerated growth of voids at grain-boundaries, which is usually a concern in conventional Fe-base alloys under conditions of inert-gas implantation, was not observed in the ODS alloy irradiated even to the highest dose (12000 at.ppm Ne). The reason is ascribed to the enhanced recombination of point defects and strong trapping of Ne atoms at the interfaces of the nano-scale oxide particles in grains. The study showed that ODS alloys have good resistance to the high-temperature inter-granular embrittlement due to inert-gas accumulation, exhibiting prominence of application in harsh situations of considerable helium production at elevated temperatures like in a fusion reactor.

Zinc oxide films with c-axis preferred orientation were deposited on silicon (100) substrates by radio frequency (RF) reactive sputtering. The properties of the samples were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy and fluorescent-spectrophotometer. The effect of sputtering power and substrate temperature on the structural and photoluminescent (PL) properties of the ZnO films was investigated. The results indicated that when the sputtering power is 100 W and the substrate temperature is 300–400°C, it is suitable for the growth of high c-axis orientation and small strain ZnO films. A violet peak at about 380 nm and a blue band at about 430 nm were observed in the room temperature photoluminescence spectra, and the origin of blue emission was investigated.

In the present work specimens of mono-crystalline silicon carbide (4H polytype) were irradiated to three successively increasing ion fluences ranging from 7.2 × 10 14 to 6.0 × 10 16 ions/cm 2 (corresponding to the peak displacement damage of 1, 4 and 13 dpa) with Ne and Xe ions respectively with the energy of 2.3 MeV/amu. The irradiated specimens were subsequently annealed at temperatures of 1173 and 1273 K. Defect structure was investigated with transmission electron microscopy (TEM) using a cross-sectional specimen preparation technique. The typical microstructures of the annealed specimens irradiated with Ne or Xe ions to high fluences are characterized by small gas bubbles in high concentration in the peak damage region and black dots and dislocation loops (located in the basal plane) in a shallower and broader depth region. Larger dislocation loops were observed in the Xe-ion irradiated specimen than in the Ne-ion irradiated specimen at the same peak damage level. The enhanced formation of dislocation loops in the case of Xe-ion irradiation is understandable by assuming stronger inclination of heavier inert-gas atoms to occupy substitute site in the peak damage region.

Thermally grown amorphous SiO2 samples were implanted at room temperature (RT) with 120 keV C-ions to a dose ranging from 1.0 × 1016 to 8.6 × 1017C ions/cm2, then irradiated at RT with 950 MeV Pb, 345 or 1754 MeV Xe ions to a fluence in the region from 1.0 × 1011 to 3.8 × 1012 ions/cm2, respectively. The irradiated samples were investigated using micro-FTIR and micro-Raman spectroscopes. It was found that new chemical bonds such as Si–C, C C(O), C C and Si(C)–O–C bonds formed significantly in the C-doped SiO2 films after heavy ion irradiations. The evolution of Si–O–C bonds and possible mechanism of structural modification in C-doped SiO2 induced by swift heavy ion irradiations were discussed.

In the present work p-type Si specimens were implanted with Cl ions of 100 keV to successively increasing fluences of 1 × 1015, 5 × 1015, 1 × 1016 and 5 × 1016 ions cm−2 and subsequently annealed at 1073 K for 30 min. The microstructure was investigated with the transmission electron microscopy (TEM) in both the plane-view and the cross-sectional view. The implanted layer was amorphized after chlorine implantation even at the lowest ion fluence, while re-crystallization of the implanted layer occurs on subsequent annealing at 1073 K. In the annealed specimens implanted above the lowest fluence three layers along depth with different microstructures were found, which include a shallow polycrystalline porous layer, a deeper single-crystalline layer containing high density of gas bubbles, a well separated deeper layer composed of dislocation loops in low density. With increasing ion fluence the thickness of the porous polycrystalline layer increases. It is indicated that chlorine can suppress the epitaxial re-crystallization of implanted silicon, when the implant fluence of Cl ions exceeds a certain level.

In this work a study of damage production in gallium nitride via elastic collision process (nuclear energy deposition) and inelastic collision process (electronic energy deposition) using various heavy ions is presented. Ordinary low-energy heavy ions (Fe+ and Mo+ ions of 110 keV), swift heavy ions (Pb-208(27+) ions of 1.1 MeV/u) and slow highly-charged heavy ions (Xen+ ions of 180 keV) were employed in the irradiation. Damage accumulation in the GaN crystal films as a function of ion fluence and temperature was studied with RBS-channeling technique, Raman scattering technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For ordinary low-energy heavy ion irradiation, the temperature dependence of damage production is moderate up to about 413 K resulting in amorphization of the damaged layer. Enhanced dynamic annealing of defects dominates at higher temperatures. Correlation of amorphization with material decomposition and nitrogen bubble formation was found. In the irradiation of swift heavy ions, rapid damage accumulation and efficient erosion of the irradiated layer occur at a rather low value of electronic energy deposition (about 1.3 keV/nm(3)),. which also varies with irradiation temperature. In the irradiation of slow highly-charged heavy ions (SHCI), enhanced amorphization and surface erosion due to potential energy deposition of SHCI was found. It is indicated that damage production in GaN is remarkably more sensitive to electronic energy loss via excitation and ionization than to nuclear energy loss via elastic collisions. (c) 2006 Elsevier B.V. All rights reserved.

Highly oriented pyrolytic graphite (HOPG) samples were irradiated by Xe ions of initial kinetic energy of 3 MeV/u. The irradiations were performed at temperatures of 500 and 800 K. Scanning tunneling microscopy (STM) images show that the tracks occasionally have elongated structures under high-temperature irradiation. The track creation yield at 800 K is by three orders of magnitude smaller compared to that obtained during room-temperature irradiation. STM and Raman spectra show that amorphization occurs in graphite samples irradiated at 500 K to higher fluences, but not at 800 K. The obtained experimental results clearly reveal that the irradiation under high temperature causes track annealing.

This paper presents the vulnerabilities of single event effects (SEEs) simulated by heavy ions on ground and observed on SJ-5 research satellite in space for static random access memories (SRAMs). A single event upset (SEU) prediction code has been used to estimate the proton-induced upset rates based on the ground test curve of SEU cross-section versus heavy ion linear energy transfer (LET). The result agrees with that of the flight data.

In order to investigate the structural stability of fullerene (C 60 ) under swift heavy ion irradiation, the irradiation experiments of thin C 60 films were performed with 22 MeV/amu Fe 56 ions delivered by HIRFL at Lanzhou in China. The irradiated C 60 films were analyzed by means of Raman scattering and Fourier transform infrared (FTIR) spectroscopes. The analysis results indicated that the damage cross-sections σ of the C 60 molecule deduced from the data of the Raman spectra are between 1.1 and 4.5 × 10 −14 cm 2 for the electronic energy loss from 3.5 to 8.7 keV/nm and electronic energy transfer dominates the damage process of C 60 films. The partial recovery of the damage in irradiated C 60 films at certain electronic energy loss is attributed to an annealing effect of strong electronic excitation.

In the present work, 120 keV N-ion doped and 30 MeV C60 ion irradiated graphite-like-carbon samples were characterized by RBS, micro-FTIR, micro-Raman, XPS spectroscopy and the variation of the properties of the samples with the N-dopant and/or C60 irradiation fluence have been studied. The RBS spectra showed that C60 irradiation can induce a partial diffusion of N atoms to the surface and the amount of the diffused N atoms increases slightly with increasing C60 irradiation fluence. The FTIR and Raman spectra exhibit characteristic bands of carbon nitrogen bonds showing that the C and N atoms are chemically bonded. The amount of chemically bonded C and N atoms increases with increasing N-dopant. By deconvolution of the XPS spectra, the atomic concentration of N and C atoms were obtained and it was identified that the samples mainly consist of three phases, namely, C3N4, CNx and tetrahedral amorphous carbon. The effect of N-dopant and C60 irradiation fluence on the modification of the properties of the samples is also discussed.

To describe the role of electronic energy loss (dE/dX)e for chemical modification of polyimide (PI), multi-layer stacks (corresponding to different dE/dX) were irradiated by different swift heavy ions (1.158 GeV Fe56 and 1.755 GeV Xe136) under vacuum and at room temperature. Chemical changes of modified PI films were studied by Fourier transform infrared (FTIR) spectroscopy. The chain disruption rate of PI was investigated in the fluence range from 1 × 1011 to 6 × 1012 ions/cm2 and a wider energy stopping power range (2.2–5.1 keV/nm for Fe56 ions and 8.6–11.5 keV/nm for Xe136 ions). Alkyne formation was observed over the electronic energy loss range of interest. By applying the saturated track model assumption (the damage process only occur in a cylinder of area σ), the mean degradation and alkyne formation radii in tracks were induced for Fe and Xe ion irradiation, respectively. The results were validated by the thermal-spike model. The analysis of the irradiated PI films shows that the predictions of the thermal-spike model of Szenes are in qualitative agreement with the curve shape of experimental results.

In this paper, the formation of the new phase and chemical bonds in N-doped diamond films after swift heavy ion irradiations was studied. The original samples were diamond films grown on (1 1 1) oriented p-Si by CVD deposition. These samples were implanted with 100 keV N-ions at room temperature to 5 × 10 17 , 1 × 10 18 and 5 × 10 18 N/cm 2 , irradiated with 345 MeV Xe or 2.64 GeV U ions, and then analyzed by means of RBS, micro-FTIR, micro-Raman and XRD spectroscopy. The obtained results suggested that N-sp 2 C and N-sp 3 C bonds formed in all N-doped diamond films, CN bond exists in all 5 × 10 18 N/cm 2 doped samples but could not form in the 5 × 10 17 N/cm 2 doped samples. In the 1 × 10 18 N/cm 2 doped sample, CN bond could form only after swift heavy ion irradiation. Intense energy deposition from the incident swift heavy ions induces the increase of sp 3 /sp 2 bonding ratio and thus enhances the formation of N-sp 3 C bonds in the samples. Furthermore, the X-ray diffraction analysis indicated that there existed new phases, α- and β-C 3 N 4 in the N-doped diamond samples after irradiation by swift heavy ions.

To describe the damage process of polymer in the energetic heavy ion tracks by thermal spike model, polycarbonate (PC, Makrofol KG) foil stacks were irradiated with various swift heavy ions (1.158 GeV Fe56, 1.755 GeV Xe136 and 2.636 GeV U238) in a very wide electronic stopping power range (from 1.9 to 17.1 keV/nm) and fluence range from 1 × 1010 to 3 × 1012 ions/cm2. The amorphous processes and chemical degradation in the irradiated PC were studied by X-ray diffraction and Fourier transform infrared spectroscopy measurements. By applying the saturated track model, the mean damage radii of tracks of the amorphous and alkyne formation process were obtained for Fe, Xe and U ion irradiation, respectively. The results were validated by the thermal spike model. The analysis of the irradiated PC films shows that the predictions of the thermal spike model of Szenes are basically in quantitative agreement with the experimental results.

Highly oriented pyrolytic graphite was irradiated with swift heavy ions (Ne, Cr, Fe, Ni, Zn, Xe and U) of fluences between 10 11 and 10 14 ions/cm 2 in energy range MeV–GeV. The combination of scanning tunneling microscopy (STM) and Raman spectroscopy studies shows that large numbers of tracks protrude from the surface. The disordered crystal lattice is leading to a Raman-active D mode. Quantitative analysis of the peak intensity indicates that the size of the crystallite domain is larger than the mean distance between in-plane tracks observed by STM. � 2003 Elsevier B.V. All rights reserved.

Polycarbonate (Makrofol kg) film stacks were irradiated by 15.14 MeV/amu Xe-136 and 11.4 MeV/amu U-238 in the electronic stopping power range (7.6-17.1 keV/nm) and the fluence range from 9 x 10(9) to 1 x 10(12) ions/cm(2). The chemical degradation of the function group was investigated by Fourier-transform infrared (FTIR) spectroscopy and the crystallinity was analyzed by X-ray diffraction (XRD) measurement. FTIR results reveal that the material suffers serious degradation after irradiation. The alkyne group was found after irradiation and their formation cross-sections were evaluated. XRD measurements show the decrease of the main XRD peak intensity, confirming that the material to be amorphised under irradiation. The ion induced amorphisation cross-section was extracted from the fitting of the experimental data for different electronic energy loss irradiations. The degradation cross-section, the formation cross-section and the amorphisation cross-section versus electronic energy loss were discussed. (C) 2002 Elsevier B.V. All rights reserved.

One hundred and twenty keV C-ion doped SiO2 films were irradiated at RT with swift Ar, Kr, Xe or U ions and their photoluminescence (PL) properties were examined. From the obtained results, we found that an intense blue–violet PL band centred at ∼435±10 nm was formed in all ion irradiated samples and a weak ultraviolet PL band centred at ∼380 nm was formed only in the samples after Kr, Xe or U ion irradiations. The PL peak intensity of the blue–violet band (i) increases with the increase of the swift heavy ion irradiation fluence, (ii) decreases with the increase of electronic energy loss Se when Se 4.85 keV/nm. Furthermore, the peak central position of the blue–violet PL is shifted slightly to violet with increasing Se and some substructures appeared in the PL spectra of the samples irradiated with Xe or U ions. The appearance of these substructures is due to the high electronic energy loss. For the violet PL band, the intensity increases with Se. Possible origins and formation mechanism of light-emitters corresponding to the observed PL bands are discussed.

The effect of ion incident angle on multiple-bit upset (MBU) has been investigated for static random access memory IDT71256. The test pattern dependent MBU ratio can be as high as 70% when tested by either normal incident 136Xe ions or 36Ar ions incident at large angles. The increase of single event upset cross-section at large angles for light ions are mainly due to occurrence of high-ratio MBU. Charges collected through funnel effect play an important role in inducing MBU in NMOS IDT71256. The MBU ratio is in proportional to energy deposited in whole sensitive layer, but the ratios of more than 2-bit upset is decided by lateral distribution of charges.

In the present work, a novel technique, “low energy ion implantation+high-energy heavy ion irradiation”, was used to synthesis light-emitting material. Experimentally, thermal-grown SiO 2 films were firstly implanted with 120 keV C + ions at room temperature (RT) to total doses in the range of (5.0×10 16 –1.0×10 18 ) ions/cm 2 . These C-doped SiO 2 films were then irradiated at RT with 335 and 855 MeV 40 Ar or 1.98 GeV 84 Kr ions to a fluence of 1.0×10 12 ions/cm 2 , or with 1.75 GeV 136 Xe ions to 1×10 11 , 5×10 11 or 1×10 12 ions/cm 2 , respectively. By measuring photoluminescence (PL) spectra of these samples excited by 320 nm light, the PL bands were investigated as functions of implantation ion dose, irradiation ion fluence and electronic energy loss S e . It was found that this technique is a useful tool to produce high quality light-emission structures, and that high-energy heavy ion irradiated C-doped SiO 2 films should be an efficient blue–violet emitting material. Furthermore, S e plays a dominant role in the formation of the PL bands, and proper C-dopant and suitable irradiation fluence will enhance the PL efficiency. Possible origins of the blue-violet PL bands formed in the ion irradiated C-doped SiO 2 films were discussed.

In this paper we present experimental results on irradiation effects of C 60 films induced by 2.0 GeV Xe 136 ions, delivered by HIRFL at Lanzhou of China. The irradiated C 60 films were analyzed by means of Fourier transform infrared, Raman scattering and X-ray diffraction spectroscopies. The analysis results indicated that electronic energy transfer dominates the damage process of C 60 films. The partial recovery of the damage in irradiated C 60 films at certain electronic energy loss is attributed to an annealing effect of strong electronic excitation. The ion velocity also plays a role in the process of the damage creation.

In order to observe the role of electronic energy loss (d E /d X ) e on chemical modification of polyimide (PI), the multi-layer stacks (corresponding to different d E /d X ) were irradiated by different swift heavy ions (1.37 GeV Ar 40 , 1.98 GeV Kr 84 , 1.755 GeV Xe 136 and 2.636 GeV U 238 ) under vacuum and room temperature. The chemical changes of modified PI films were studied by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) absorption spectroscopy. The degradation of PI was investigated in the fluence range from 1×10 10 to 5.5×10 12 ions/cm 2 and different electronic energy loss from 0.77 to 11.5 keV/nm. The FTIR results show the absorbance of the typical function group decrease exponentially as a function of fluence. The alkyne end group was found after irradiation and its formation radii were 5.6 and 5.9 nm corresponding to 8.8 and 11.5 keV/nm Xe irradiation respectively. UV/Vis analysis indicates the radiation induced absorbance change follows a linear relation as function of fluence corresponding to various ion and the production efficiency of the chromophores depends strongly on the electronic energy loss (d E /d X ) e with a power relation.

Polymer films including polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) were irradiated at room temperature with ions of 35 MeV/u 40Ar, 25 MeV/u 84Kr, 15.1 MeV/u 136Xe and 11.4 MeV/u 238U to fluences ranging from 9×109 to 5.5×1012 ions/cm2. The radiation-induced chemical changes of the materials were investigated by Fourier-transform infrared (FTIR) and ultraviolet/visible spectroscopies. It is found that the absorbance in the ultraviolet and visible range induced by all irradiations follows a linear relationship with fluence. The radiation-induced absorbance normalized to one particle increases slowly with increasing of electronic energy loss below about 8 keV/nm followed by a sharp increase up to about 15 keV/nm above which saturation is reached. FTIR measurements reveal that the materials suffer serious degradation through bond breaking. The absorbance of the typical infrared bands decays exponentially with increase of ion fluence and the bond-disruption cross-section shows a sigmoid variation with electronic energy loss. In PET loss of crystallinity is attributed to the configuration transformation of the ethylene glycol residue from trans into the gauche. Alkyne end groups are induced in all the materials above certain electronic energy loss threshold, which is found to be about 0.8 keV/nm for PS and 0.4 keV/nm for PC. The production cross-section of alkyne end group increases with increasing of electronic energy loss and shows saturation at high electronic energy loss values. It is concluded that not only the physical processes but also the chemical processes of the energy deposition determine the modification of polymer.

Polyethylene terephthalate films were irradiated with high-energy heavy ions to fluences ranging from 9×10 9 to 5.5×10 12 ions/cm 2 . The radiation-induced changes in molecular and crystalline structures were investigated by the Fourier-transform infrared (FTIR) spectroscopy and the X-ray diffraction measurement. FTIR spectra measurements reveal that the material suffers serious degradation through bond breaking. The absorbance of the typical infrared bands decays exponentially with increase of ion fluence and the bond-disruption cross-section shows a sigmoid variation with the electronic energy loss. The semi-crystalline structure of the material is destroyed by the irradiation with processes that are electronic energy loss dependent. At lower electronic energy loss values the amorphization is closely related to the destruction of the trans-configuration of the ethylene glycol residue. At high electronic energy loss, however, other processes determine the amorphization.

A novel technique,‘‘low energy ion implantation þ swift heavy ion irradiation’’,was used to synthesize lightemitting materials. In the present work,SiO 2 films were implanted with 120 keV C þ ions at room temperature (RT) to total doses from 5:0 � 10 16 to 1:0 � 10 18 ions/cm 2 ,and then irradiated at RT with swift Xe or U ions to different irradiation fluences. Photoluminescence (PL) spectra of these samples were measured at RT and intense blue–violet PL bands were observed. The properties of the PL bands were analyzed as a function of implantation ion dose,swift heavy ion irradiation fluence and electronic energy loss of the irradiation ion in the sample. The possible origins of the observed blue and violet emissions were also discussed. 2002 Elsevier Science B.V. All rights reserved.

SiO2 thin films were implanted at room temperature (RT) with 120 keV carbon ions to a dose of 1.0×10 17 ions / cm 2 and then irradiated at RT with high-energy 84Kr or 40Ar ions to a fluence of 1.0×10 12 ions / cm 2 . Using 320 nm monochromatic ultra-violet light for excitation, photoluminescence (PL) properties of these samples were examined and intense blue PL bands were observed. It was found that the blue PL peak intensity changes with electronic energy loss of the irradiation ion in the sample. With increasing the electronic energy loss level, the PL peak intensity decreases and the peak position shifts towards to the short-wavelength direction. Furthermore, the existence of C-dopants enhances the luminescence property of the irradiated samples.

Si1-xCx alloys of carbon (C) concentration between 0.6%-1.0% were grown in Si by ion implantation and high temperature annealing. The formation of Si1-xCx alloys under different ion doses and their stability during annealing were studied. If the implanted dose was less than that for amorphizing Si crystals, the implanted C atoms would like to combine with defects produced during implantation and it was difficult to form Si1-xCx alloys after being annealed at 850 degreesC. With the increment of implanted C ion doses, the lattice damage increased and it was easier to form Si1-xCx alloys. But the lattice strain would become saturate and only part of implanted carbon atoms would occupy the substitutional positions to form Si1-xCx alloys as the implanted carbon dose increased to a certain degree. Once Si1-xCx alloys were formed, they were stable at 950 degreesC, but part of their strain would release as the annealing temperature increased to 1 000 degreesC. Stability of the alloys became worse with the increment of carbon concentration in the alloys.

In this work, a solution-annealed specimen of a low-activation Fe-Cr-Mn alloy was irradiated with 92 MeV Ar ions at 450 degreesC to a dose of 1.7 x 10(21) m(-2) which was expected to produce a peak displacement damage of 90 dpa. After irradiation, damage microstructure was investigated from the cross-sectional specimens using a transmission electron microscope. High number density cavities were observed in the peak dose region. Size of cavities was the largest at the peak displacement damage. Formation of alpha -phase was found at a grain boundary in the peak dose region. Well-dispersed carbide particles was found in the matrix. The carbide/matrix interfaces supplied favorable site for growth of large cavities, whereas only small cavities were found inside the particles. (C) 2000 Elsevier Science B.V. Ail rights reserved.

Semicrystalline polyethylene terephthalate (PET) foil stacks were irradiated with 1.373 GeV Ar ions to different fluences ranging from 1.0×1010 to 5.0×1012 ions/cm2. The induced effects were investigated by means of the Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible absorption spectroscopy (UV/VIS) and electron spin resonance spectroscopy (ESR). FTIR measurements show that bond breaking processes are mainly observed at the ethylene glycol residue of trans configuration and at the para position of benzene rings above a critical dose of about 4.0 MGy. Damage cross-section has been extracted for the band at 973 cm−1 from the dependence of the absorbance on fluence and it shows a linear dependence on the mean electronic energy loss. UV/VIS measurements show a strong increase in absorbance in the ultraviolet and visible regions. It is found that for the same absorbed dose, more increase in absorbance is induced at higher electronic energy loss. ESR measurements indicate the creation of free radicals. The radical concentration is found to increase rapidly with the increasing absorbed dose above 4.0 MGy.

Investigation of the surface modification in molecular structure of semicrystalline polyethylene terephthalate (PET) films induced by Ar ion bombardment is presented. The PET samples are analysed by using Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS). A significant loss of crystallinity is observed, which is related to the configuration transformation of ethylene glycol residue from the trans into the gauche. Chain scissions are observed at the para position of di-substituted benzene rings, –CO bonds and C–O bonds. The C–O bonds are destroyed more selectively than –CO bonds. The benzene ring structures show only small change under irradiation and do not participate in degradation process. Extra CC bonds and alkyne end groups are created above a critical dose of 4.0 MGy. The results are briefly discussed.

A variety of recent experiments in metallic targets unambiguously prove that a dense electron excitation induces atomic displacements leading to bulk damage. However, till now there is no convincing theoretical model that explains these. In the present work, a model based on the thermal spike mechanism has been proposed to account for the experimental evidence and a microscopic energy transfer mechanism between excited electrons and target atoms. This model follows four stages in the time scale of events: (1) ejection of target electrons and atoms, (2) slowing down of ejected electrons and thermalization of target valence electrons, (3) conversion of energy from thermalized electrons to target atoms, and (4) structural modification of the target. The characteristics of energy transfers are indirect and coherent in space and time. Based on mathematical developments of this model, electronic energy loss-induced thermal spike process and accompanying defect evolution are numerically simulated. In a collective process involving many neighboring target atoms, this thermal spike process is sufficient to result in microstructure modification in the bulk of metallic materials. Therefore, in the framework of this model, experimental results available in metallic materials can be explained.

Polystyrene (PS) films of about 53 μm in thickness are stacked together and are irradiated with 1.37 GeV Ar ions at room temperature to fluences ranging from 1.1 × 1010 to 5.5 × 1012 cm−2. The radiations induced chemical changes are studied by the Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) spectroscopies. It is found that the material undergoes serious degradation under irradiation and the chemical modifications depend strongly on the electronic energy loss. The main chains of PS as well as the phenyl ring are destroyed in the track core simultaneously with a damage cross-section of about 28.6 nm2. Significant reduction in the absorbance of bands at 1602, 2853 and 3059 cm−1 occurs above about 0.77 keV/nm at an energy deposition of about 6.4 MGy. The stronger reduction in intensity of the band at 706 cm−1 compared to the band at 1602 cm−1 is partly attributed to cross-links outside the track core. Alkynes are produced above a threshold of about 0.77 keV/nm. The progressive shift of the absorption edge from UV towards the visible is attributed to the carbonization of the material.

Polystyrene (PS) films are irradiated at room temperature with 3 MeV silicon ions and 1.4 GeV argon ions to fluences ranging from 1×10 10 to 3×10 14 cm −2 . Fourier transform infrared (FTIR) specula reflection spectra and ultraviolet/visible (UV/Vis) transmission spectra are measured to investigate the radiation-induced chemical modifications. It is found that the intrinsic absorption bands show reduction in intensity with increasing fluence and electronic energy loss, indicating the degradation of the polymeric structure. For Si ion implanted specimens, significant chemical modifications occur above about 3×10 13 cm −2 , corresponding to an average energy deposition of about 45 MGy. For Ar ion irradiated specimens, the critical electronic energy loss is around 0.77 keV/nm at the fluence of 5.5×10 12 cm −2 , corresponding to an energy deposition of about 6.4 MGy. The increase in absorbance in the UV/Vis range and a shift of the absorption edge toward the visible is attributed to carbonization of the material. The results are discussed on the basis of ion fluence and energy loss.