Transmission Electron Microscopy Inspection Research Articles

Unfolding an Elusive Area-Selective Deposition Process: Atomic Layer Deposition of TiO2 and TiON on SiN vs SiO2.

Area-selective atomic layer deposition (AS-ALD) processes for TiO2 and TiON on SiN as the growth area vs SiO2 as the nongrowth area are demonstrated on patterns created by state-of-the-art 300 mm semiconductor wafer fabrication. The processes consist of an in situ CF4/N2 plasma etching step that has the dual role of removing the SiN native oxide and passivating the SiO2 surface with fluorinated species, thus rendering the latter surface less reactive toward titanium tetrachloride (TiCl4) precursor. Additionally, (dimethylamino)trimethylsilane was employed as a small molecule inhibitor (SMI) to further enhance the selectivity. Virtually perfect selectivity was obtained when combining the deposition process with intermittent CF4/N2 plasma-based back-etching steps, as demonstrated by scanning and transmission electron microscopy inspections. Application-compatible thicknesses of ∼8 and ∼5 nm were obtained for thermal ALD of TiO2 and plasma ALD of TiON.

Enhanced deformability of WE43 magnesium alloy by activation of non-basal slip and twinning deformation modes in the equal channel angular pressing at room temperature

Activation of the prismatic and pyramidal slip systems, along with the twinning as the secondary deformation mechanism, assists in the accommodation of a larger plastic strain during the deformation of magnesium alloys. In this paper, deformation mode activity and texture evolution of the WE43 magnesium alloy were investigated during core-sheath equal channel angular pressing (ECAP) at room temperature. Texture studies and transmission electron microscopy inspections suggest that the mechanisms behind the ECAP at room temperature assisted by back pressure were activation of (101¯0) prismatic slip (as the primary mechanism), as well as extension and contraction twinning.

Simultaneous enhancement of powder properties, additive manufacturability, and mechanical performance of Ti–6Al–4V alloy by 2D-nanocarbon decoration

Poor understanding of composite powder properties is a bottleneck in the design of high-performance metallic components via laser powder bed fusion (L-PBF). Traditional particle- or fiber-like fillers are known to result in reduced powder flowability and the uncontrollable morphology of composite powders. In this work, we demonstrate a first example of improving the powder properties and L-PBF manufacturability of metallic powders decorated by two-dimensional (2D) nanofillers. 0.5 wt% graphene oxide (GO) sheets were uniformly adhered onto the surface of Ti–6Al–4V (Ti64) powders via an electrostatic self-assembly, with their spherical morphology and particle size uncompromised. The notably enhanced quality of the GO-decorated Ti64 (GO@Ti64) powder bed, indicated by the results of a novel centrifugal separation testing and a recoating experiment, was attributed to the significant reduction in powder/powder and powder/substrate adhesive forces. Moreover, while the thermal conductivity of the GO@Ti64 powders was found to decrease, the laser absorptivity increased as a result of multiple local absorptions of wrinkled GO. The optimal process zone of GO@Ti64 powders was therefore shown to have been extended and to have become wider, enhancing L-PBF printability. High-resolution transmission electron microscopy inspections revealed that the GO/Ti64 build fully consisted of ultrafine α’ martensite structures with a lath width of ∼91 nm. This novel structure was attributed to the high-temperature, nonequilibrium densification of L-PBF; the complete dissolution of the 2D GO nanosheets into the Ti64 matrix generated a novel carbon-supersaturated, precipitation-free structure. The grain refinement and solid-solution strengthening behaviors led to an increase in the yield strength of the GO/Ti64 build from 1375 MPa to 1793 MPa, and also an increase in its compressive strength, from 1796 MPa to 2032 MPa. The results of this investigation contribute to a better understanding of composite powder properties and can be seen as a significant step toward the preparation of high-performance metallic components via L-PBF.

Monolithic Integration of Nano-Ridge Engineered InGaP/GaAs HBTs on 300 mm Si Substrate.

Nano-ridge engineering (NRE) is a novel method to monolithically integrate III–V devices on a 300 mm Si platform. In this work, NRE is applied to InGaP/GaAs heterojunction bipolar transistors (HBTs), enabling hybrid III-V/CMOS technology for RF applications. The NRE HBT stacks were grown by metal-organic vapor-phase epitaxy on 300 mm Si (001) wafers with a double trench-patterned oxide template, in an industrial deposition chamber. Aspect ratio trapping in the narrow bottom part of a trench results in a threading dislocation density below 106∙cm−2 in the device layers in the wide upper part of that trench. NRE is used to create larger area NRs with a flat (001) surface, suitable for HBT device fabrication. Transmission electron microscopy inspection of the HBT stacks revealed restricted twin formation after the InGaP emitter layer contacts the oxide sidewall. Several structures, with varying InGaP growth conditions, were made, to further study this phenomenon. HBT devices—consisting of several nano-ridges in parallel—were processed for DC and RF characterization. A maximum DC gain of 112 was obtained and a cut-off frequency ft of ~17 GHz was achieved. These results show the potential of NRE III–V devices for hybrid III–V/CMOS technology for emerging RF applications.

Gas vesicle isolated from microorganisms to act as ultrasound contrast agent

Ultrasound contrast agent (UCA), used to enhance the contrast in ultrasonography, consists of microbubbles filled with an inert gas and encapsulated with a protein or a lipidic-stabilize membrane. The UCAs are able to resonate when exposed to ultrasound waves and to generate an echo-acoustic signal with increased intensity. Recently, a technique to produce UCA from microorganisms was developed and it consists of lysing microorganism cells to obtain gas vesicle (GV) after cultivation in the laboratory. GVs occur almost exclusively in aquatic microorganisms, as Microcystis aeruginosa (MYC), and provide buoyancy which permit to float towards the water surface. This work implemented a technique to produce GVs from MYC, at the Ultrasound Laboratory, and inspected their properties of acting as UCAs, analyzed through ultrasonic images acquired at 40 MHz, and their structural characteristics such as morphology, diameter, and length. After the cultivation of MYC, the buoyant cells with GVs were separated from the culture medium and submitted to cell lysis with chemical treatment. Thereafter, the solution with lysed cells was centrifuged, at 300g during 8 h at 4–8 °C, to isolate the GVs (absorbance 0.6, λ = 500 nm). Transmission electron microscopy inspection revealed the MYC-GVs with elliptical morphology and having a diameter between 100 and 150 nm and length near to 200 nm. B-mode ultrasound images of the solutions proved the GV’s ability to generate an echo signal, thus confirming their performance as UCAs.

Antibacterial activity of chitosan against Burkholderia pseudomallei.

The ability of Burkholderia pseudomallei to persist and survive in the environment is a health problem worldwide. Therefore, the antibacterial activities of chitosan against four environmental isolates of B. pseudomallei from soil in Khon Kaen, Thailand, were investigated. Antibacterial activities were assessed by a plate count technique after treatment with 0.2, 0.5, 1, 2 or 5 mg ml−1 chitosan for 0, 24 and 48 hr. Chitosan at 5 mg ml−1 completely killed all four B. pseudomallei isolates within 24 hr, whilst 2 mg ml−1 chitosan lowered the viability of B. pseudomallei by 20% within the same time span. Chitosan may act by disruption of the cell membrane, releasing intracellular components that can be detected spectrophotometrically at 260 and 280 nm. Transmission electron microscopy inspection of chitosan‐treated B. pseudomallei revealed damage to the bacterial membranes. This study demonstrated the effective antibacterial activity by chitosan against B. pseudomallei. Chitosan causes disruption of the bacterial cell membrane, release of intracellular constituents and cell death. This study revealed the inhibitory potential of chitosan for mitigating B. pseudomallei occurrences.

Deformation-induced amorphization and austenitization in white etching area of a martensite bearing steel under rolling contact fatigue

The paper investigated the composition and the formation mechanism of white etching areas (WEAs) generated in rolling contact fatigue (RCF) of a bearing steel using scanning electron microscopy (SEM) transmission electron microscopy (TEM). It is generally accepted that WEA consists of nano ferrites. However, the current study revealed that nano ferrite is not the final product of the WEA. Instead, it involves phase transformation and amorphization. TEM inspection showed the WEA exhibits an amorphous phase with martensite, austenite and carbides embedded interior. The amount of austenite is greatly increased in the WEA, indicating a phase transformation from martensite to austenite. The analysis showed that both the amorphization and the austenitization are proceeded under a shear-induced mechanism. Asa result of partial amorphization, nanocrystallites and amorphous phase coexist. Various morphologies are present in the WEA.

High-performance nanocomposites synergistically reinforced by two-dimensional montmorillonite and zero-dimensional nanoTiO2

Comprehensive high-performance epoxy nanocomposites were successfully prepared by co-incorporating two-dimensional montmorillonite (MMT) and zero-dimensional nanoTiO2 into epoxy. Mechanical tests and thermal analyses showed that the resulting epoxy/MMT/nanoTiO2 nanocomposites obtained great improvements over pure epoxy, epoxy/MMT nanocomposites, and epoxy/nanoTiO2 nanocomposites in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature. The best performance occurred with the nanocomposite containing 5 phr MMT/nanoTiO2. At this loading, the tensile modulus increased by 154.75, 35.69, and 89.56%, the tensile strength by 81.53, 143.46, and 22.01%, the flexural modulus by 21.12, 6.04, and 3.31%, the flexural strength by 25.25, 16.98, and 9.73%, the notch impact strength by 65.57, 37.23, and 25.94%, the glass transition temperature by 11.3, 12.2, and 11.4 °C, and the thermal decomposition temperature by 15.3, 3.0, and 3.2 °C as compared with those of pure epoxy, 5 phr epoxy/MMT nanocomposite and 5 phr epoxy/nanoTiO2 nanocomposite, respectively. X-ray diffraction and transmission electron microscopy inspection revealed that in the epoxy/MMT/nanoTiO2 nanocomposites, the MMT was completely exfoliated into two-dimensional nanoscale mono-platelets, which formed special intermingled structure with the zero-dimensional nanoTiO2 spheres. This study suggests that co-incorporating two proper, dimensionally different nanomaterials into polymer matrices could be a pathway to success in preparing comprehensive high-performance polymer nanocomposites.

Integration of porous low-k dielectrics using post porosity pore protection

Post porosity pore protection is studied as a means for low damage integration of porous low-k dielectrics. Homogeneous low-k densification is achieved using poly(methyl methacrylate) (PMMA) as a sacrificial filler. The improvement in plasma-induced damage is investigated on a plasma-enhanced chemical vapor deposition 2.0 porous organo-silicate glass, including damage from radicals and vacuum ultraviolet photons. Open pores are sealed upon polymer protection; therefore the penetration of metal species during deposition of a metal diffusion barrier is avoided. Various solutions for post metallization polymer removal are investigated, such as hydrogen remote plasma and an ultraviolet cure. The PMMA removal process is studied in order to avoid Cu wire degradation. Finally, low-k damage and barrier continuity are investigated on patterned wafers with functional circuits. By means of transmission electron microscopy inspection and electrical measurement, effective integrated k-values are extracted, giving a value keff ~ 2.5–2.6 for the post metallization polymer removal option.

Electron back-scattered diffraction and nanoindentation analysis of nanostructured Al tubes processed by multipass tubular-channel angular pressing

Microstructural evolution and mechanical properties of nanostructured 1060 aluminum alloy tubes processed by tubular-channel angular pressing (TCAP) process were investigated using electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM) and nanoindentation analyzes. EBSD scans revealed a homogeneous ultrafine grained microstructure after the third passes of the TCAP process. Apart from that the mean grain sizes of the TCAP processed tubes were refined to 566 nm, 500 nm and 480 nm respectively after the first, second and third passes. The results showed that after the three TCAP passes, the grain boundaries with a high angle comprised 78% of all the boundaries. This is in comparison to the first pass processed sample that includes approximately 20% HAGBs. The TEM inspection afforded an appreciation of the role of very low-angle misorientation boundaries in the process of refining microstructure. Nanoindentation results showed that hardness was the smallest form of an unprocessed sample while the largest form of the processed sample after the three passes of TCAP indicated the highest resistant of the material. In addition, the module of elasticity of the TCAP processed samples was greater from that of the unprocessed sample.

Properties and growth peculiarities of Si0.30Ge0.70 stressor integrated in 14 nm fin-based p-type metal-oxide-semiconductor field-effect transistors

Integration of Si0.30Ge0.70 in the Source/Drain (S/D) areas of metal oxide semiconductor transistors built according to 14nm technological node rules has been shown. SiGe properties and growth peculiarities are presented and elaborated. In order to preserve the fin structures during a pre-epitaxy surface preparation, the H2 bake pressure had to be increased to 19,998Pa at 800°C. Influence of this bake on the Si recess in the S/D areas is presented. Excellent quality of both the raised and the embedded Si0.30Ge0.70 was demonstrated by transmission electron microscopy inspections. Energy-dispersive X-ray spectroscopy measurement showed two stages of SiGe growth for the embedded case: first with a lower Ge content at the beginning of the deposition until the (111) facets are formed, and second with a higher Ge content which is governed by the growth on (111) planes. Nano-beam diffraction analysis showed that SiGe grown in the S/D areas of p-type metal-oxide-semiconductor field-effect transistor is fully elastically relaxed in the direction across the fin and partially strained along the fin. Finally, a strain accumulation effect in the chain of transistors has been observed.

Effect of focused ion beam deposition induced contamination on the transport properties of nano devices

Focused ion beam (FIB) deposition produces unwanted particle contamination beyond the deposition point. This is due to the FIB having a Gaussian distribution. This work investigates the spatial extent of this contamination and its influence on the electrical properties of nano-electronic devices. A correlation study is performed on carbon-nanotube (CNT) devices manufactured using FIB deposition. The devices are observed using transmission electron microscopy (TEM) and these images are correlated with device electrical characteristics. To discover how far Pt-nanoparticle contamination occurs along a CNT after FIB electrical contact deposition careful TEM inspections are performed. The results show FIB deposition efficiently improves electrical contact; however, the practice is accompanied by serious particle contamination near deposition points. These contaminants include metal particles and amorphous elements originating from precursor gases and residual water molecules in the vacuum chamber. Pt-contamination extends for approximately 2 μm from the point of FIB contact deposition. These contaminants cause current fluctuations and alter the transport characteristics of devices. It is recommended that nano-device fabrication occurs at a distance greater than 2 μm from the FIB deposition of an electrical contact.

Highly Improved Gaseous Hydrogen Storage Characteristics of the Nanocrystalline and Amorphous Nd–Cu-added Mg2Ni-type Alloys by Melt Spinning

The nanocrystalline and amorphous Mg–Nd–Ni–Cu quaternary alloys with a composition of (Mg 24 Ni 10 Cu 2 ) 100− x Nd x ( x = 0–20) were prepared by melt spinning. The X-ray diffraction and transmission electron microscopy inspections reveal that, by varying the spinning rate and the Nd content, different microstructures could be obtained by melt spinning. Particularly, the as-spun Nd-free alloy holds an entire nanocrystalline structure but the as-spun Nd-added alloy has a nanocrystalline and amorphous structure, which implies that the addition of Nd facilitates the glass forming in the Mg 2 Ni-type alloy. Also, the degree of the amorphization in the as-spun Nd-added alloys clearly increases with increasing the spinning rate and the Nd content. The H-storage capacity and the hydrogenation kinetics of amorphous, partially and completely nanocrystalline alloys were investigated and it was found that they are dependent on the microstructure and the phase composition of the alloys. Specially, enhancing the spinning rate from 0 (the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s makes the hydrogen absorption saturation ratio ( R 5 a ) (a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increase from 35.2% to 90.3% and the hydrogen desorption ratio ( R 10 d ) (a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rise from 12.7% to 44.9% for the ( x = 5) alloy. And the growing of the Nd content from 0 to 20 gives rise to the R 5 a and R 10 d values rising from 85.7% to 94.5% and from 36.7% to 54.8% for the as-spun (30 m/s) alloys, respectively.

Short-wavelength undulatory extinction in quartz recording coseismic deformation in the middle crust – an experimental study

Abstract. Deformation experiments are carried out on natural vein quartz in a modified Griggs-type solid medium apparatus to explore the preservation potential of microfabrics created by crystal-plastic deformation at high stress, overprinted during subsequent creep at lower stress. A corresponding stress history is expected for the upper plastosphere, where fault slip during an earthquake causes quasi-instantaneous loading to high stress, followed by stress relaxation. The question is whether evidence of crystal-plastic deformation at high stress, hence an indicator of past seismic activity, can still be identified in the microstructure after overprint by creep at lower stresses. First, quartz samples are deformed at a temperature of 400 °C and constant strain rate of 10−4 s−1 ("kick"), and then held at 900 to 1000 °C at residual stress ("creep"). In quartz exclusively subject to high-stress deformation, lamellar domains of slightly differing crystallographic orientation (misorientation angle < 2°) and a few tens of micrometres wide occur. In the transmission electron microscope (TEM), these areas show a high density of tangled dislocations and cellular structures. After "kick and creep" experiments, pronounced short-wavelength undulatory extinction (SWUE) is observed in the polarization microscope. The wavelength of SWUE is up to 10 μm, with oscillatory misorientation of up to a few degrees. TEM inspection reveals domains with high density of dislocations and differing diffraction contrast bound by poorly ordered dislocation walls. Only zones with exceptional damage generated during high-stress deformation are replaced by small new grains with a diameter of about 10 to 20 μm, forming strings of recrystallized grains. For large original grains showing SWUE, the Schmid factor for basal ⟨ a ⟩ glide is found to be high. SWUE is taken to reflect high-stress crystal-plastic deformation, the modified microstructure being sufficiently stable to be recognized after subsequent creep as an indicator of past seismic activity.

Aerosol Synthesis and Reactivity of Thin Oxide Shell Aluminum Nanoparticles via Fluorocarboxylic Acid Functional Coating

There is currently a need for low oxide content nanoaluminum as a component in high‐energy‐density fuels. A gas‐phase passivation coating of perfluoropentanoic acid on in situ generated bare nanoaluminum accomplished in an aerosol stream and resulting in an air‐stable product is demonstrated. Transmission electron microscopy inspection demonstrates a 1–2 nm coating layer, and thermogravimetric analysis reveals an 80% active fuel content, an increase of 17% from untreated product. X‐ray photoelectron spectroscopy confirms both the presence of the fluorocarboxylic acid on the aluminum surface and the thinner coating layer compared with the untreated case. A bridge bonding coordination between the carboxylate group and aluminum is indicated via Fourier transform infrared spectroscopy. The coated product demonstrates reduced ignition temperature in thermite combinations for temperature‐jump fine wire combustion tests and X‐ray photoelectron spectroscopy verifies formation of AlF3 in burned product.

Single-cell lysis for visual analysis by electron microscopy

The stochastic nature of biological systems makes the study of individual cells a necessity in systems biology. Yet, handling and disruption of single cells and the analysis of the relatively low concentrations of their protein components still challenges available techniques. Transmission electron microscopy (TEM) allows for the analysis of proteins at the single-molecule level. Here, we present a system for single-cell lysis under light microscopy observation, followed by rapid uptake of the cell lysate. Eukaryotic cells were grown on conductively coated glass slides and observed by light microscopy. A custom-designed microcapillary electrode was used to target and lyse individual cells with electrical pulses. Nanoliter volumes were subsequently aspirated into the microcapillary and dispensed onto an electron microscopy grid for TEM inspection. We show, that the cell lysis and preparation method conserves protein structures well and is suitable for visual analysis by TEM.

Oxidation study on as-bonded intermetallic of copper wire–aluminum bond pad metallization for electronic microchip

In this work, influence of Copper free air ball (FAB) oxidation towards Intermetallic Compound (IMC) at Copper wire–Aluminum bond pad metallization (Cu/Al) is studied. Samples are synthesized with different Copper FAB oxidation condition by turning Forming Gas supply ON and OFF. Studies are performed using Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and line-scan Energy Dispersive X-ray (EDX). SEM result shows there is a cross-sectional position offset from center in sample synthesized with Forming Gas OFF. This is due to difficulty of determining the position of cross-section in manual grinding/polishing process and high occurrence rate of golf-clubbed shape of oxidized Copper ball bond. TEM inspection reveals that the Copper ball bond on sample synthesized with Forming Gas OFF is having intermediate oxidation. Besides, the presence of IMC at the bonding interface of Cu/Al for both samples is seen. TEM study shows voids form at the bonding interface of Forming Gas ON sample belongs to unbonded area; while that in Forming Gas OFF sample is due to volume shrinkage of IMC growth. Line-scan EDX shows the phases present in the interfaces of as-bonded samples are Al4Cu9 (∼3 nm) for sample with Forming Gas ON and mixed CuAl and CuAl2 (∼15 nm) for sample with Forming Gas OFF. Thicker IMC in sample with Forming Gas OFF is due to cross-section is positioned at high stress area that is close to edge of ball bond. Mechanical ball shear test shows that shear strength of sample with Forming Gas OFF is about 19% lower than that of sample with Forming Gas ON. Interface temperature is estimated at 437 °C for as-bonded sample with Forming Gas ON by using empirical parabolic law of volume diffusion.

Cathode-Control Alloying at an Au-ZnSe Nanowire Contact via in Situ Joule Heating

Controllable interfacial alloying is achieved at a Au-ZnSe nanowire (M-S) contact via in situ Joule heating inside transmission electron microscopy (TEM). TEM inspection reveals that the Au electrode is locally molten at the M-S contact and the tip of the ZnSe nanowire is covered by the Au melting. Experimental evidences confirm that the alloying at the reversely biased M-S contact is due to the high resistance of the Schottky barrier at this M-S contact, coincident to cathode-control mode. Consequently, in situ Joule heating can be an effective method to improve the performance of nanoelectronics based on a metal-semiconductor-metal nanostructure.

Effects of oxygen bonding on defective semiconducting and metallic single-walled carbon nanotube bundles

We report the effects of oxygen doping on the electrical properties of defective metallic and semiconducting single-walled carbon nanotube bundles. Carbon vacancies are generated by electron beam knock-out process. The carbon nanotube bundles are placed on top of suspended electrodes produced on a through-hole chip. This allows a physical correlation to be established for transmission electron microscopy inspection and electrical characterization. The dangling carbon bonds of the vacancies are very active and can easily adsorb oxygen molecules. In terms of the semiconducting bundles, oxygen bonding lowers the bandgap and the original p-type bundles thereby modifying them to become bi-polar. For the metallic bundles, a hysteretic bi-stable state in gate-voltage cycling is observed; this is attributed to the electrically controlled dipole field of the oxygen molecules.

Comprehensive high‐performance epoxy nanocomposites co‐reinforced by organo‐montmorillonite and nano‐SiO2

AbstractComprehensive high‐performance epoxy nanocomposites were successfully prepared by co‐incorporating organo‐montmorillonite (o‐MMT) and nano‐SiO2 into epoxy matrix. Because of the strong interaction between nanoscale particles, the MMT layers were highly exfoliated, and the exfoliated nanoscale MMT monoplatelets took an interlacing arrangement with the nano‐SiO2 particles in the epoxy matrix, as evidenced by X‐ray diffraction measurement and transmission electron microscopy inspection. Mechanical tests and thermal analyses showed that the resulting epoxy/o‐MMT/nano‐SiO2 nanocomposites improved substantially over pure epoxy and epoxy/o‐MMT nanocomposites in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature. This study suggests that co‐incorporating two properly selected nanoscale particles into polymer is one pathway to success in preparing comprehensive high‐performance polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012