Secondary Ion Mass Spectrometry Results Research Articles

Improvement of the properties and electrical performance on TiCl 4-based TiN film using sequential flow chemical vapor deposition process

Sequential flow chemical vapor deposition (SFCVD), utilizing TiCl 4/NH 3 as reactants and immediate NH 3 treatment after film deposition, is applied to produce TiN barrier films in the contact process. Secondary ion mass spectroscopy results indicate that the SFCVD TiN film can effectively block the diffusion of WF 6 into the underlying Ti layer during W deposition. NH 3 treatment immediately after film deposition causes SFCVD TiN films to be less contaminated with carbon than TiN films that are formed by metallic organic compounds chemical vapor deposition (MOCVD) and to contain less chlorine residue than conventional TiCl 4/NH 3 CVD TiN layers even at a low reaction temperature. According to the resistance measurement of Kelvin contacts, the SFCVD process yields a lower resistance and a more uniform distribution than the MOCVD or CVD process. Transmission electron microscopic observations demonstrate that WF 6 can diffuse through the MOCVD TiN to react with the underlying Ti layer, causing a rupture at the Ti/TiN interface and poor W adhesion. The SFCVD TiN can serve as a sufficient diffusion barrier against WF 6 penetration during W CVD deposition.

Oxidation characteristics of Ti 3AlC 2 over the temperature range 500–900 °C

Titanium aluminium carbide (Ti 3AlC 2) displays a unique combination of characteristics of both metals and ceramics coupled with an unusual combination of mechanical, electrical and thermal properties. In this research, the oxidation characteristics of Ti 3AlC 2 over the temperature range 500–900 °C were studied by synchrotron radiation diffraction (SRD) and secondary-ion mass spectrometry (SIMS) experiments which provided elemental and phase compositional depth profiles over this range. Evidence for the outward diffusion of Al during oxidation was shown for the first time by the complementary SIMS results, which suggested the existence of amorphous Al or aluminium oxide at low temperature oxidation. At 500 °C, only anatase-TiO 2 was detected by SRD in addition to the parent Ti 3AlC 2. Transformation of anatase to rutile was observed at 600 °C and was completed by 900 °C. The crystalline phase α-Al 2O 3 was detected at 900 °C but not at lower temperatures.

Phosphorus-doped silicon quantum dots for all-silicon quantum dot tandem solar cells

Doping of Si quantum dots is important in the field of Si quantum dots-based solar cells. Structural, optical and electrical properties of Si QDs formed as multilayers in a SiO 2 matrix with various phosphorus (P) concentrations introduced during the sputtering process were investigated for its potential application in all-silicon quantum dot tandem solar cells. The formation of Si quantum dots was confirmed by transmission electron microscopy. The addition of phosphorus was observed to modify Si crystallization, though the phosphorus concentration was found to have little effect on quantum dot size. Secondary ion mass spectroscopy results indicate minimal phosphorus diffusion from Si QDs layers to adjacent SiO 2 layers during high-temperature annealing. Resistivity is significantly decreased by phosphorus doping. Resistivity of slightly phosphorus-doped (0.1 at% P) films is seven orders of magnitude lower than that of intrinsic films. Dark resistivity and activation energy measurements indicate the existence of an optimal phosphorus concentration. The photoluminescence intensity increases with the phosphorus concentration, indicating a tendency towards radiative recombination in the doped films. These results can provide optimal condition for future Si quantum dots-based solar cells.

Accurate measurement and evaluation of the nitrogen depth profile in plasma nitrided iron

Nitrogen depth profile of plasma nitrided pure iron was measured and evaluated by accurate experimental techniques. Plasma nitriding cycles were carried out on high purity iron substrate in an atmosphere of 75% H 2–25% N 2. Nitrogen concentration depth profiles in the compound layer and the diffusion zone were characterized by glow discharge optical emission spectroscopy (GDOES) and secondary ion mass spectroscopy (SIMS), respectively. Nitrogen diffusion depths were measured accurately by optical and scanning electron microscopy as well as SIMS technique at different nitriding times. Experimental results indicated good agreement between SIMS data and microscopic evaluations for various nitriding cycles. The results of SIMS showed the nitrogen diffusion depth of about 2000 μm in the diffusion zone for 10 h plasma nitriding at 550 °C. Such high depth had not been detected in previous investigations in which the conventional methods such as EDS, GDS, XPS, EPMA or ion probe techniques were used.

Role of silicon on the growth mechanisms of CN x and SiCN thin films by N 2/CH 4 microwave plasma assisted chemical vapour deposition

CN x and SiCN thin films were deposited by microwave plasma assisted chemical vapour deposition on Si, Si/Si 3N 4 and WC-Co/Si substrates in a N 2/CH 4 gas mixture. The source of silicon was the substrate itself. Its role in the growth of CN x and SiCN is not well understood yet. To better understand the surface mechanisms involved in the film growth, as well as the role played by the silicon, some films are synthesized on WC-Co cermets and WC-Co recovered by a variable thickness silicon layer. Morphological analyses realized by scanning electron microscopy and transmission electron microscopy show that the obtained films are made of nano-crystalline grains with size ranging between 20 and 70 nm. The X-ray diffraction spectrum and selected area electron diffraction patterns exhibits a signature that could correspond to beta-C 3N 4, cubic-C 3N 4 and cubic-SiCN. The films deposited on WC-Co substrates are compared to those, which are synthesized on Si and Si/Si 3N 4 substrates. We have observed that the deposition of a continuous film was impossible on non-silicon contain (WC-Co) substrates, and only carbon balls were obtained on a such substrate. Otherwise, the deposition becomes possible if a silicon underlayer is deposited on to the WC-Co substrates. The films are close to those synthesized with Si or Si/Si 3N 4 substrates. In all cases, the growth stops as soon as a thin film is deposited on the substrate and the plasma cannot access to the silicon underlayer. Finally, a growth mechanism showing that silicon takes part of the deposition and improves the nitrogen ratio in the films is proposed. Regarding the energy dispersion X-ray spectroscopy and secondary ion mass spectroscopy results, it seems that the incorporation of nitrogen is activated only by the presence of silicon, which behaves as a catalyst.

Effects of AlAs interfacial layer on material and optical properties of GaAs∕Ge(100) epitaxy

Ga As ∕ Al As ∕ Ge ( 100 ) samples grown at 650°C with AlAs interfacial layer thickness of 0, 10, 20, and 30nm were characterized using transmission electron microscopy, secondary ion mass spectrometry (SIMS), and photoluminescence (PL) techniques. SIMS results indicate that the presence of an ultrathin AlAs interfacial layer at the GaAs∕Ge interface has dramatically blocked the cross diffusion of Ge, Ga, and As atoms, attributed to the higher Al–As bonding energy. The optical quality of the GaAs epitaxy with a thin AlAs interfacial layer is found to be improved with complete elimination of PL originated from Ge-based complexes, in corroboration with SIMS results.

Post-annealing temperature dependence of blistering in high-fluence ion-implanted H in Si 〈1 0 0〉

This study examined the influence of post-annealing temperature on blister formation and growth in ion-implanted H in Si 〈100〉. Ion energy levels of 40 and 100keV and fluences of 2×1016 and 5×1016cm−2 were investigated. Post-annealing treatments were performed using the furnace annealing (FA) method with temperatures ranging from 200 to 600°C for a duration of 1h. Raman scattering spectroscopy (RSS), optical microscopy (OM), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (XTEM) were employed to explore the mechanisms behind the smart cut technique. The results revealed that variations among the transformation of the VH3 (or V2H6) defect complex phase into the Si(100):H bonding configuration phase (RSS results), the appearance of optically detectable blisters and craters (OM results), the average depth of craters (AFM results), the trapping of hydrogen atoms and gettering of oxygen atoms (SIMS results), and the damaged microstructures (XTEM results) against post-annealing temperature were in close correspondence. It was also found that the optimal post-annealing temperature for blister formation and growth was 550°C.

Formation of Aluminum Hydride during Alkaline Dissolution of Aluminum

The role of hydrogen-containing surface species in the alkaline dissolution of aluminum was studied by secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM). The measurements revealed quasi-periodic nucleation and dissolution of large number densities of size particles, during open-circuit dissolution in NaOH(D) at room temperature. SIMS results using deuterated solutions, and prior Auger microprobe measurements, indicated that the particles were composed of aluminum hydride (deuteride), with an aluminum hydroxide (deuteroxide) surface layer. The measured open-circuit potential during dissolution was close to the Nernst potential of hydride oxidation. It was concluded that forms continuously during dissolution by reaction of cathodically generated hydrogen with the Al metal and is oxidized to aluminate ions in the accompanying anodic process. The present results are a direct confirmation of hydride formation on Al accompanying corrosion.

Rearrangement of the oxide-semiconductor interface in annealed Al2O3∕4H-SiC structures

Al 2 O 3 films with different thicknesses have been deposited on n-type (nitrogen-doped) 4H-SiC(0001) epitaxial samples by atomic layer chemical vapor deposition at 300°C and subsequently annealed in Ar atmosphere at temperatures up to 1000°C. The Al2O3∕4H-SiC structures were analyzed by x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and transmission electron microscopy (TEM). The XPS and SIMS results indicate that the average composition in the wider interface area does not significantly change due to the annealing. However, as revealed by the TEM investigations in combination with XPS, the as-grown samples exhibit a double interface created by an intermediate suboxide SiOx layer (x<2). After annealing, this intermediate suboxide layer breaks up and transforms into SiO2 islands, resulting in a rather rough interface region and a high concentration of pure Si in the Al2O3 film. Furthermore, a pronounced accumulation of H is found in the rough interface region and this may play a key role for the low density of shallow electron states reported for annealed Al2O3∕4H-SiC structures.

Dynamic Simulation of Vapor Transport Equilibration in Congruent LiNbO3 Crystal

Vapor transport equilibration (VTE) in a congruent lithium niobate (LiNbO3) plate is modeled using the implicit finite difference method, and Li-diffusion at 1100 °C in both Z-cut and X-cut plates with thicknesses from 0.5 to 3 mm is simulated for VTE duration up to 450 h. Li-diffusivity at 1100 °C was determined experimentally based upon secondary-ion-mass spectrometry (SIMS) analysis. A good agreement of numerical results with SIMS results or optical absorption edge measurement results confirms the accuracy of the Li-diffusivity and the validity of the VTE model proposed and the numerical method employed. The mutual influence problem of two VTE processes from the top and the bottom surfaces of the plate and the VTE duration needed to fully VTE-treat a plate are discussed in relation to the crystal's cut and thickness. The VTE duration dependence on the mean Li/Nb ratio within a 20 μm depth is studied.

Growth of a Novel Periodic Structure of SiC/AlN Multilayers byLow Pressure Chemical Vapour Deposition

A novel 10-period SiC/AlN multilayered structure with a SiC cap layeris prepared by low pressure chemical vapour deposition (LPCVD). Thestructure with total film thickness of about 1.45 μm is depositedon a Si (111) substrate and shows good surface morphology with a smallerrms surface roughness of 5.3 nm. According to the secondary ion massspectroscopy results, good interface of the 10 period SiC/AlN structureand periodic changes of depth profiles of C, Si, Al, N components areobtained by controlling the growth procedure. The structure exhibitsthe peak reflectivity close to 30% near the wavelength of 322 nm. Tothe best of our knowledge, this is the first report of growth of theSiC/AlN periodic structure using the home-made LPCVD system.

Effects of thermal annealing on In-induced metastable defects in InGaN films

We investigated the effects of thermal annealing on the properties of InGaN layers. From secondary ion mass spectroscopy results, it was found that severe In desorption occurred after annealing. Photoluminescence and X-ray diffraction results indicate that significant amounts of In vacancy-related defects exist in the annealing samples. It was also found that persistent photoconductivity decay time constants were 211, 893 and 1040 s, while the decay exponents were 0.153, 0.120 and 0.213 for the as-grown, 800 °C-annealed and 1000 °C-annealed InGaN epitaxial layers, respectively.

Stability and effect of annealing on the optical properties of plasma-deposited Ta2O5 and Nb2O5 films

Tantalum and niobium oxide optical thin films were prepared at room temperature by plasma-enhanced chemical vapor deposition using tantalum and niobium pentaethoxide (M(OC2H5)5) precursors. We studied the evolution of their optical and microstructural properties as a result of annealing over a broad temperature range from room temperature up to 900 °C. The as-deposited films were amorphous; their refractive index, n, and extinction coefficient, k, at 550 nm were n=2.13 and k<10−4 for Ta2O5, and n=2.24 and k<10−4 for Nb2O5. The films contained a small amount of residual carbon (∼ 2–6 at.%) bonded mostly to oxygen. During annealing, the onset of crystallization was observed at approximately TC1=650 °C for Ta2O5 and at TC1=450 °C for Nb2O5. Upon annealing close to T1 (300 °C for Nb2O5 and 400 °C for Ta2O5), n at 550 nm decreased by less than 1%. This was correlated with the decrease of carbon content, as suggested by Fourier transform infrared spectroscopy, elastic recoil detection and static secondary ion mass spectroscopy (SIMS) results. During annealing, we observed phase transition from the δ- (hexagonal) phase to the L- (orthorhombic) phase between 800 °C and 900 °C for Ta2O5, and between 600 °C and 700 °C for Nb2O5. The structural changes were also marked by silicon diffusion from the substrate into the oxide layer at annealing temperatures above 500 °C for Ta2O5 and above 400 °C for Nb2O5. As a consequence of oxygen, silicon and metal interdiffusion, the interface between the Si substrate and the metal oxide (Ta2O5 or Nb2O5) is characterized by its broadening, well documented by spectroscopic ellipsometry and SIMS data.

Nitrogen incorporation in GaNAs layers grown by molecular beam epitaxy

Ga N As ∕ Ga As quantum wells with high N concentrations, grown by molecular beam epitaxy, have been investigated by secondary-ion mass spectrometry (SIMS), high resolution x-ray diffraction (XRD), and photoluminescence (PL) measurements. The substitutional N concentration in an 18nm thick strained GaNAs layer varies from 1.4% to 5.9% when the growth rate is reduced from 1to0.2μm∕h. By further reducing the growth rate, more N can be incorporated but relaxation occurs. Both the total N concentration, deduced from SIMS measurements, and the substitutional N concentration, deduced from XRD measurements, increase with reduced growth rate. By comparing the SIMS and XRD results, we found that a large amount of N was not in substitutional position when the substitutional N concentration is high (&amp;gt;4%). The experimental results also show that there is no detectable change of total and substitutional N concentrations, within the instrument resolutions, after rapid thermal annealing at 700°C for 30s. However, PL measurements show a strong blueshift of the emission wavelength after annealing and the PL intensity increases by more than one order of magnitude.

Hydroxyl in mantle olivine xenocrysts from the Udachnaya kimberlite pipe

The incorporation of hydrogen in mantle olivine xenocrysts from the Udachnaya kimberlite pipe was investigated by Fourier-transform infrared spectroscopy and secondary ion mass spectrometry (SIMS). IR spectra were collected in the OH stretching region on oriented single crystals using a conventional IR source at ambient conditions and in situ at temperatures down to −180°C as well as with IR synchrotron radiation. The IR spectra of the samples are complex containing more than 20 strongly polarized OH bands in the range 3,730–3,330 cm−1. Bands at high energies (3,730–3,670 cm−1) were assigned to inclusions of serpentine, talc and the 10 A phase. All other bands are believed to be intrinsic to olivine. The corresponding point defects are (a) associated with vacant Si sites (3,607 cm−1E || a, 3,597 E || a, 3,571 cm−1E || c, 3,567 E || c, and 3,556 E || b), and (b) with vacant M1 sites (most of the bands polarized parallel to a). From the pleochroic behavior and position of the OH bands associated with the vacant M1 sites, we propose two types of hydrogen—one bonded to O1 and another to O2, so that both OH vectors are strongly aligned parallel to a. The O2–H groups may be responsible for the OH bands at higher wavenumbers than those for the O1–H groups. The multiplicity of the corresponding OH bands in the spectra can be explained by different chemical environments and by slightly different distortions of the M1 sites in these high-pressure olivines. Four samples were investigated by SIMS. The calculated integral molar absorption coefficient using the IR and SIMS results of 37,500±5,000 L mol H2O cm−2 is within the uncertainties slightly higher than the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003) (28,450±1,830 L mol H2O cm−2). The reason for the difference is the different distributions of the absorption intensity of the spectra of both studies (mean wavenumber 3,548 vs. 3,570 cm−1). Olivine samples with a mean wavenumber of about 3,548 cm−1 should be quantified with the absorption coefficient as determined in this study; those containing more bands at higher wavenumber (mean wavenumber 3,570 cm−1) should be quantified using the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003).

Precise analysis of H, C, N, and O as dominant impurities in Cu films: complementary use of SIMS and GDMS

Secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS) were used to determine the impurity concentrations of hydrogen, carbon, nitrogen, and oxygen elements in Cu films, and the results of SIMS and GDMS were carefully interpreted. The Cu films were deposited on Si (100) substrates at substrate bias voltages ranging from 0 V to −150 V using a non-mass separated ion beam deposition method. From the results of SIMS using a Cs− ion beam, as a whole, many high intensity peaks were observed in the Cu films deposited without substrate bias voltage. From the quantitative GDMS results, these peaks were determined to be signals detected as a cluster state such as CxHx, OxHx, CxOxHx. Therefore, using a combination of these dominant impurities, all the unknown peaks observed in the SIMS results could be interpreted. Moreover, it was found that the dominant impurities having a great influence on the film purity were hydrogen, carbon, nitrogen, and oxygen.

Optimization and Structural Characterization of W/Al2O3 Nanolaminates Grown Using Atomic Layer Deposition Techniques

W/Al2O3 nanolaminates were fabricated using atomic layer deposition (ALD) techniques. ALD of tungsten was performed using alternating exposures of WF6 and Si2H6. ALD of Al2O3 was performed using alternating exposures of Al(CH3)3 and H2O. The fabrication of optimum nanolaminates was very dependent on nucleation during the ALD of each layer. The nucleation of Al2O3 ALD on W surfaces and W ALD on Al2O3 surfaces was examined using quartz crystal microbalance investigations. Al2O3 ALD on W nucleated easily during the first Al(CH3)3/H2O reaction cycle. In contrast, W ALD nucleation on Al2O3 required multiple WF6/Si2H6 reaction cycles and was very sensitive to the Si2H6 exposure. The W ALD nucleation required at least six or seven WF6/Si2H6 reaction cycles. The optimum reaction parameters for nucleation were utilized to fabricate W/Al2O3 nanolaminates with a total targeted thickness of ∼1000 Å that were composed of various numbers of bilayers. Transmission electron microscopy (TEM) images revealed very well defined two-bilayer and four-bilayer W/Al2O3 nanolaminates grown at 177 °C. Depth-profile secondary ion mass spectrometry (SIMS) measurements confirmed the composition of the W/Al2O3 nanolaminates. Both the TEM and SIMS results showed that sharper interfaces were observed when W ALD nucleates on Al2O3, and rougher interfaces were observed when Al2O3 ALD nucleates on W. X-ray reflectivity (XRR) investigations indicated that the W/Al2O3 nanolaminates were much thicker than the ∼1000 Å target for the total thickness when the W/Al2O3 nanolaminates were composed of a larger number of bilayers. These results were consistent with much lower than expected film densities for the thin Al2O3 ALD nanolayers. Atomic force microscope studies revealed that the surface roughness of W/Al2O3 nanolaminates was lower at lower growth temperatures and lower at higher interfacial densities. XRR investigations also revealed a pronounced Bragg peak with a high X-ray reflectivity from 64-bilayer W/Al2O3 nanolaminates grown at 177 °C. The X-ray reflectivity of the 64-bilayer W/Al2O3 nanolaminates grown at 177 °C was constant versus annealing up to 500 °C. The reflectivity then dropped rapidly for annealing at ≥600 °C. This thermal instability will place some limits on the application of W/Al2O3 nanolaminates as thermal barrier coatings and X-ray mirrors.

Ion beam analysis of urban aerosol micro and nanoparticles compared with environmentally related children diseases in two Polish towns

Urban aerosol particles were collected in two Polish towns—Legnica and Starachowice, and characterised with mass spectrometry methods. Bulk analysis of particulate matter collected on quartz fibre filters was performed using spark source mass spectrometry (SSMS). Analysis of chosen elements revealed the differences in total concentrations in the towns. We found in Legnica more: Sr—5 times with respect to Starachowice, Se, As—3 times, Cl, V, Y, Mo—2 times, Cr, Fe, Ni, Cu, Rb i Pb—less than 2 times. In Starachowice we found more: Ti—40 times, Zn—5 times, Mn—2 times, Br, Co i Zr—less than 2 times. Another technique—secondary ion mass spectrometry (SIMS) allowed us to perform depth profile analysis of collected particles on aluminium plates of cascade impactor. The SIMS results showed “core-shell” structure of particles dependent on their grain size in the range of 300 nm to 15 μm. The shell layer was enriched in Cr, Cu and Pb. The results were compared with the medical study of the prevalence of environmentally related children diseases observed in these two cities. Questionnaire studies and allergic skin prick tests were performed according to the protocol of International Study of Asthma and Allergies in Childhood (ISAAC). An epidemiological study performed on Legnica and Starachowice children shows statistically similar results besides the compositional and morphological differences of particles suspended in the air of the two towns.

O 18 tracer diffusion in Pb(Zr,Ti)O3 thin films: A probe of local oxygen vacancy concentration

A series of O18 tracer in-diffusion experiments have been conducted on state-of-the-art metal organic chemical vapor deposition–grown Pb(Zr,Ti)O3 (PZT) films. Prior to O18 incorporation, samples were preequilibrated in O216 at the same temperature and total pressure used for the following O218 isotope exchange anneal. The final O18 depth profiles were obtained using secondary ion mass spectroscopy (SIMS), which provides a depth resolution of 3–5Å. The SIMS results indicate that the O18 tracer diffusivity varies as a function of depth from the PZT film surface in a way that is inconsistent with a combined grain boundary and lattice diffusion mechanism. Based on a previously-developed model for point defect equilibrium in metal titanate thin films, simulations of O18 tracer diffusion into PZT thin films that are consistent with the experimental results are described.

Comparison of experimental and theoretical results of nitrogen implantation in AISI 304 stainless steel

Depth and distribution of implanted ions play an important role in electrical and mechanical properties of implanted surfaces. In this study nitrogen implantation at 30keV with different doses in the range of 1 × 1017–1 × 1018ions/cm2 on AISI 304 stainless steel samples has been performed. The experimental and theoretical depth profiles of nitrogen-implanted samples are investigated. Experimental depth profile using secondary ion mass spectrometry (SIMS) is compared with theoretical analysis (TRIM simulation). By considering the presence of N2+ in the implanting ion beam and sputtering effects, the TRIM and SIMS results were modified to good agreement. The proper ratio of N2+/N+ is evaluated by a curve fitting procedure.