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Showing papers in "Journal of Vacuum Science and Technology in 1995"


Journal ArticleDOI
TL;DR: In this article, a variety of PPA surfaces have been prepared using identical single-layer and double-layer NSL masks made by self-assembly of polymer nanospheres with diameter, D =264 nm, and varying both the substrate material S and the particle material M. In the examples shown here, S was an insulator, semiconductor, or metal and M was a metal, inorganic ionic insulator or an organic π-electron semiconductor.
Abstract: In this article nanosphere lithography (NSL) is demonstrated to be a materials general fabrication process for the production of periodic particle array (PPA) surfaces having nanometer scale features. A variety of PPA surfaces have been prepared using identical single‐layer (SL) and double‐layer (DL) NSL masks made by self‐assembly of polymer nanospheres with diameter, D=264 nm, and varying both the substrate material S and the particle material M. In the examples shown here, S was an insulator, semiconductor, or metal and M was a metal, inorganic ionic insulator, or an organic π‐electron semiconductor. PPA structural characterization and determination of nanoparticle metrics was accomplished with atomic force microscopy. This is the first demonstration of nanometer scale PPA surfaces formed from molecular materials.

1,470 citations


Journal ArticleDOI
TL;DR: In this paper, a detailed discussion of the method is presented including consideration of the types of materials and the electronic energy states involved, e.g., Fermi edges, vacuum levels, etc., and the couplings that must exist for the referencing method to be correctly applied.
Abstract: It has become common practice to employ, as a binding energy reference for x‐ray photoelectron spectroscopy studies on nonconductive materials, the C(1s) spectra of the ubiquitous (adventitious) carbon that seems to exhibit an instantaneous presence on all air exposed materials. Despite this commonality, surface scientists, including many practitioners, have expressed substantial concerns about the validity of this approach. A detailed discussion of the method is presented including consideration of the types of materials and the electronic energy states involved, e.g., Fermi edges, vacuum levels, etc., and the couplings that must exist for the referencing method to be correctly applied. A number of other surface environments for which the carbon referencing method may be fallacious are also presented. This leads to a consideration of the electron spectroscopy for chemical analysis results for different types of adventitious species and how the presence of some of these may confuse the use of the method. In this regard, we will also discuss the use of other methods to establish binding energy scales, such as Fermi edge coupling and select doping (e.g., the Au dot approach).

653 citations


Journal ArticleDOI
TL;DR: In this article, a volume averaged model of high-density plasma discharges in molecular gases was developed for low and high pressures and for electropositive and electronegative plasmas.
Abstract: We develop a global (volume averaged) model of high‐density plasma discharges in molecular gases. For a specified discharge length and diameter, absorbed power, pressure, and feed gas composition, as well as the appropriate reaction rate coefficients and surface recombination constants, we solve the energy and particle balance equations to determine all species densities and the electron temperature. We use an expression for charged particle diffusive loss that is valid for low and high pressures and for electropositive and electronegative plasmas. We apply the model to Ar, O2, Cl2, and Ar/O2 discharges and compare with available experimental data. In Ar, we find that the ion density increases monotonically with increasing pressure, while for O2 and Cl2, the total positive ion density increases initially, then decreases as pressure is further increased. For a pure Cl2 discharge, we find that surface recombination processes are important in affecting the degree of dissociation and the negative‐ion density of the system. For mixtures of Ar and O2, we find that at a fixed ratio of Ar to O2 flowrates, the dominant ionic species changes from Ar+ to O+ as pressure is increased. When a small amount of Ar is added to a pure O2 discharge, the overall positive‐ion density increases, whereas the ratio of negative ion to electron density decreases.

499 citations



Journal ArticleDOI
TL;DR: In this paper, the behavior of argon plasmas driven by time modulated power in high density plasma reactors is investigated using a global model, where the time evolution of the electron temperature and the plasma density is calculated by solving the particle and energy balance equations.
Abstract: The behavior of argon plasmas driven by time modulated power in ‘‘high density’’ plasma reactors is investigated using a global model. The time evolution of the electron temperature and the plasma density is calculated by solving the particle and energy balance equations. In the first stage of power application during the ‘‘on’’ time, the electron temperature rapidly increases above the steady state value. In this region, charged particles accumulate in the plasma due to the relatively higher power applied than for the continuous wave (cw) case. In the first stage of the ‘‘off’’ time, the electron temperature drops quickly, yielding a smaller particle loss (Bohm) velocity. These effects give rise to higher time‐average plasma densities than for the cw plasma driven by the same average power. The highest average plasma density obtained was more than twice the density of the cw plasma for a duty ratio of 25%. Even higher plasma densities were obtained for shorter duty ratios. The possibility of controlling chemical reactions in the plasma by changing the modulation period is also shown.

264 citations


Journal ArticleDOI
TL;DR: In this paper, a line segment simulator incorporating ballistic deposition and minimization of chemical potential has been used to aid in the understanding of the growth mechanisms of these films and to optimize the evaporation process.
Abstract: An evaporation process has been developed for depositing highly porous insulator or metal films with densities as low as 15% of bulk. The process utilizes either multiple evaporation sources or substrate movement to provide a symmetrical but very oblique (≳80%) flux incident on the substrate. Extreme self‐shadowing produced a vertical columnar microstructure consisting of isolated and evenly spaced columns including a unique zigzag structure in a number of insulator films. Features of the film are often anisotropic, leading to conductivity differences of as much as a factor of two along perpendicular axes in the plane of the film surface. The direction of anisotropic growth was observed to switch orientation as the incident flux angle was increased to very oblique, beyond approximately 80°. A line segment simulator incorporating ballistic deposition and minimization of chemical potential has been used to aid in the understanding of the growth mechanisms of these films and to optimize the evaporation process. The simulator helped to confirm that self‐shadowing was the dominant mechanism in this porous structure formation.

255 citations


Journal ArticleDOI
TL;DR: In this paper, thin carbon-nitrogen films have been formed by direct impingement of 5-100 eV C+ and N+ or N+2 ions upon solid surfaces, as well as by 5-350 eV N+ bombardment of graphite surfaces.
Abstract: Thin carbon–nitrogen films have been formed by direct impingement of 5–100 eV C+ and N+ or N+2 ions upon solid surfaces, as well as by 5–350 eV N+ bombardment of graphite surfaces. The influences of ion energy, N+/C+ arrival rate, and type of substrate have been studied. The films deposited in this manner are found to be essentially amorphous, with some graphitic regions on the scale of a few nm. Two distinct types of C–N bonding, one attributed to graphitelike local structure (C–N π bonds) and one attributed to C3N4‐like local structure (C–N σ bonds), have been detected by x‐ray photoelectron spectroscopy. Films deposited by dual‐beam deposition and single‐beam nitridation at 75 eV or less exhibit differences in the single‐bonded structure. Total nitrogen concentrations of up to 47 at. % have been measured by Auger electron spectroscopy (AES) and Rutherford backscattering spectrometry. The C KVV Auger line shapes of the two phases have been determined by factor analysis. These line shapes are consistent ...

217 citations


Journal ArticleDOI
TL;DR: In this article, high efficient InGaN/AlGaN double-heterostructure blue-light-emitting diodes (LEDs) with an external quantum efficiency of 5.4% were fabricated by codoping Zn and Si into an active layer.
Abstract: Highly efficient InGaN/AlGaN double‐heterostructure blue‐light‐emitting diodes (LEDs) with an external quantum efficiency of 5.4% were fabricated by codoping Zn and Si into an InGaN active layer. The output power was as high as 3 mW at a forward current of 20 mA. The peak wavelength and the full width at half maximum of the electroluminescence of blue LEDs were 450 and 70 nm, respectively. Blue‐green LEDs with a brightness of 2 cd and a peak wavelength of 500 nm were fabricated for application to traffic lights by increasing the indium mole fraction of the InGaN active layer.

182 citations


Journal ArticleDOI
TL;DR: In this article, the authors found that gold surfaces are oxidized by a combination of UV light and ozone generated from a mercury lamp, and the oxide layer was found to be 17±4 A-thick by variable angle XPS depth profiling.
Abstract: Gold surfaces have been found to be hydrophilic only after exhaustive preparation and with the ultimate care in sample preparation and treatment. The use of a combination of ultraviolet (UV) light and ozone has been described as a viable method of producing a clean, hydrophilic, gold surface. We have found that gold surfaces, which have been either stored in the laboratory after vacuum deposition or purchased as high purity standards, are oxidized by a combination of UV light and ozone generated from a mercury lamp. The samples were characterized with x‐ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) prior to and after exposure to UV/ozone in a stainless steel box in laboratory air. After the cleaning process gold surfaces were found by XPS to contain less carbon and to be enriched in oxygen. The O 1s on the cleaned surface, which was not present on the untreated surface, consisted of two peaks that are attributed to gold oxide and hydroxyl. The oxide layer was found to be 17±4 A thick by variable angle XPS depth profiling with an initial stoichiometry of Au2O3. The oxide was found to be stable to extended exposure to UHV and water and ethanol rinses. ISS compositional depth profiles confirmed the oxide layer thickness and that the hydrated surface layer is removed in the initial sputtering of the oxidized gold. Implications of these results related to the mechanism of self‐assembly of thiols on gold are discussed.

164 citations


Journal ArticleDOI
TL;DR: In this article, the role of step sites on metal surfaces in promoting chemical reactions is discussed showing experimental data from the author's laboratory, and the adsorption of CO on two stepped Pt surfaces, Pt (112) and Pt (335), is compared using various methods that are sensitive to adsorptive site character.
Abstract: The role of step sites on metal surfaces in promoting chemical reactions is discussed showing experimental data from the author’s laboratory. The adsorption of CO on two stepped Pt surfaces, Pt (112) and Pt (335), is compared using various methods that are sensitive to adsorption site character. The existence of one‐dimensional arrays of chemisorbed CO molecules along the step sites is demonstrated, and CO...CO repulsive steric interactions are observed to cause orthogonal tilting of the step‐bound CO species as the coverage is changed on the step sites. For Pt (335), the most active site for the oxidation of CO is found to involve a chemisorbed oxygen atom at the step site, reacting with a CO molecule chemisorbed on a terrace site. It is also shown that a new surface phenomenon, electron stimulated migration (ESM), may be spectroscopically observed for CO on Pt (335). The atomic steps act as trap sites for CO molecules that have been excited by 150 eV electrons. It is likely that this ESM phenomenon is a property of thermally nonaccommodated species in the electronic ground state of the chemisorbed CO that have been produced by quenching from an excited electronic state.

158 citations


Journal ArticleDOI
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) is used to study carefully prepared oxide-free titanium nitride (TiN) films of nearly identical stoichiometry, grown by direct sputtering and reactive evaporation.
Abstract: X‐ray photoelectron spectroscopy (XPS) is used to study carefully prepared oxide‐free titanium nitride (TiN) films of nearly identical stoichiometry, grown by direct sputtering and reactive evaporation. The line shapes and peak positions of the Ti 2p and N 1s transitions are dependent upon the deposition method. The XPS results showed that oxynitrides are present following exposure of either type of film to dry oxygen; however, reactively evaporated films have a considerably higher oxidation rate. Differences in valence band and electron energy loss spectroscopy (EELS) spectra are correlated with the changes observed in the core levels. The EELS spectra detected the presence of a low energy loss, which is correlated with the TiN electron density of states closest to the Fermi level. The secondary electron emission yields for reactively evaporated TiN were also measured before and after dry oxygen and air exposure, and after heating. The maximum yields are about 10% lower for reactively evaporated films than for similarly treated previously measured sputter‐deposited layers.

Journal ArticleDOI
TL;DR: In this paper, high transparent and conductive amorphous zinc-stannate thin films were prepared by rf magnetron sputtering using a target with a Zn/(Zn+Sn) content of 33 at.
Abstract: Highly transparent and conductive amorphous zinc‐stannate thin films were prepared by rf magnetron sputtering using a target with a Zn/(Zn+Sn) content of 33 at. %. The resistivity distribution of the zinc‐stannate films having a composition near ZnSnO3 and deposited on the surface of substrates placed parallel to the target surface was successfully controlled by optimizing both the sputter gas pressure and oxygen partial pressure. A uniform distribution with a resistivity of 4–5×10−3 Ω cm and an average transmittance above 80% in the visible range was obtained for undoped zinc‐stannate films deposited on substrates from room temperature to 300 °C. The zinc‐stannate films were found to be thermally and chemically more stable than undoped SnO2 and ZnO films.

Journal ArticleDOI
TL;DR: In this paper, the morphology of CdTe thin films has been studied by atomic force microscopy, and the observations were correlated to results obtained from x-ray diffraction, cathodoluminescence, and minority carrier lifetime measurements.
Abstract: CdTe thin films, deposited on different substrate structures by physical vapor deposition, sputtering, and close‐spaced sublimation, have been treated with CdCl2 at several temperatures. The morphology of the films has been studied by atomic force microscopy, and the observations were correlated to results obtained from x‐ray diffraction, cathodoluminescence, and minority‐carrier lifetime measurements. The samples treated at 400 °C resulted in the best device‐quality films, independent of deposition method and underlying substrate structure. For the first time, a nanograin structure was observed in CdTe sputtered samples.

Journal ArticleDOI
TL;DR: In this article, angle-resolved x-ray photoelectron spectroscopy was used to identify the differences in surface chemical state and composition between the layers formed on the surface of TiNi alloys after mechanical polishing, chemical etching, autoclaving in water and steam, and exposure to H2O2 or air.
Abstract: In spite of the generally good biocompatibility of TiNi revealed in numerous in vivo studies, medical applications of these shape memory alloys as implants are hindered due to the lack of knowledge on the nature of their biocompatibility. Better material characterization is necessary for understanding the chemical and physical properties which determine biocompatibility. The purpose of the present investigation is to use angle‐resolved x‐ray photoelectron spectroscopy to identify the differences in surface chemical state and composition between the layers formed on the surface of TiNi alloys after mechanical polishing, chemical etching, autoclaving in water and steam, and exposure to H2O2 or air. The surface chemistry drastically depends on the preparation method; the Ni surface concentration can be varied in the range 0–30 at. %. In natural conditions (air, water, and steam) TiNi surfaces revealed a tendency to be covered by TixNiyO2x oxides (where x varies in the range of 7–20 and y varies in the range ...

Journal ArticleDOI
TL;DR: In this paper, the electron density in the ICP reactor decreases exponentially in a downstream region while the most abundant ionic species CF+ increases in proportion to the rf power with the CF+3 density almost constant.
Abstract: Comprehensive measurements of charged particles and neutral radicals in an inductively coupled plasma (ICP) are performed to understand and control the etching process using a CF4/H2 gas. The electron density in the ICP reactor decreases exponentially in a downstream region while the most abundant ionic species CF+ increases in proportion to the rf power with the CF+3 density almost constant. The neutral radical diagnostics by appearance mass spectrometry indicate 10 times more F atoms and somewhat fewer CFx radicals (x=1–3) in ICP, compared with a high‐pressure capacitively coupled plasma diode. Such a small ratio of the CFx density to the F density is possibly a cause of the low etch selectivity of SiO2 to Si in ICP etching. Two innovative methods to achieve the high selectivity in ICPs are demonstrated. One is wall heating (100–200 °C), which leads to a drastic increase in CFx densities with the F density almost constant. The other is a pulse modulation of rf power at 30–50 μs durations where the time‐...

Journal ArticleDOI
TL;DR: In this paper, thin thin films of stoichiometric, amorphous C3N4 have been prepared by means of chemical transport of carbon in intense nitrogen glow discharge at relatively high deposition temperature of about 800 °C.
Abstract: Compact thin films of stoichiometric, amorphous C3N4 have been prepared by means of chemical transport of carbon in intense nitrogen glow discharge at relatively high deposition temperature of about 800 °C. Their hardness reached 2500 Vickers (kg/mm2).

Journal ArticleDOI
TL;DR: In situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to study surface processes during plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide through tetraethoxysilane (TEOS) and oxygen as mentioned in this paper.
Abstract: In situ attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy was used to study surface processes during plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide through tetraethoxysilane (TEOS) and oxygen. ATR‐FTIR studies were conducted on thin (about 50 A) silicon dioxide films deposited on GaAs. This approach allowed us to obtain the infrared spectrum of TEOS adsorbed on SiO2 in the spectral region 4000–770 cm−1 and to determine the surface species and their relative surface concentrations as a function of deposition conditions in a helical resonator plasma reactor. Studies were conducted where the SiO2 surface was exposed to TEOS and O2 plasma sequentially and/or simultaneously. Surface processes were studied as a function of exposure to TEOS and substrate temperature. In situ ATR‐FTIR studies of adsorption of TEOS on the SiO2 surface show that TEOS adsorbs chemically and irreversibly onto the SiO2 surface above 100 °C. SiO2 growth was found to occur even without ...

Journal ArticleDOI
TL;DR: Pulsed laser deposition (PLD) has quickly emerged as a unique tool with which to grow high quality films of complex chemical compounds as mentioned in this paper, and it is estimated that at present the number of different materials which have been deposited by PLD now exceeds two hundred.
Abstract: Pulsed laser deposition (PLD) has quickly emerged as a unique tool with which to grow high quality films of complex chemical compounds. It is estimated that at present the number of different materials which have been deposited by PLD now exceeds two hundred. Scientists have used this process primarily as a laboratory tool to deposit films of various compounds that are typically difficult to synthesize by other techniques, and then quickly evaluate the relevant material properties. Deposition techniques such as ion‐beam, rf, or dc magnetron sputtering, electron‐beam evaporation, molecular beam epitaxy, chemical vapor deposition, and metal organic chemical vapor deposition, have all achieved wide‐spread acceptance as processes with which to grow various types of electronic and optical films. In order for PLD to emerge as a real production process, it must be demonstrated that PLD is capable of depositing material over useful substrate sizes with acceptable uniformity. PLD must also compete with more establ...

Journal ArticleDOI
TL;DR: In this article, a molecular dynamics study of 50 eV Ar+ ion bombardment of a Si(100) crystal with a monolayer of adsorbed chlorine was conducted to simulate atomic layer etching (ALET) of Si.
Abstract: A molecular dynamics study of 50 eV Ar+ ion bombardment of a Si(100) crystal with a monolayer of adsorbed chlorine was conducted to simulate atomic layer etching (ALET) of Si. The total reaction yield (Si atoms removed per ion) was 0.172; 84% of silicon was removed as SiCl, 8% as elemental Si and 8% as SiCl2. Based on the total yield, an ion dose of 1.16×1016 ions/cm2 is necessary to remove one monolayer of silicon. Reaction occurs during the ps time scale of the ion–solid interaction. Long time‐scale chemistry (100s of ms) which is possible in ion‐assisted etching with simultaneous exposure to neutral and ion beams does not happen in ALET. It was further found that 93% of Si originated from the top silicon layer and 7% from the layer underneath. In addition, some structural ‘‘damage’’ was induced to the top three silicon layers. It appears that perfect ALET of silicon is not possible for an ion energy of 50 eV.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated hydrogen-methane-argon plasmas and found that high argon fractions (≳50%) lead to intense C2 emission, indicating significant production of C2 in the plasma.
Abstract: It was shown recently that nanocrystalline diamond films can be grown using fullerenes as precursors in an argon microwave plasma without the addition of hydrogen or oxygen. Extensive fragmentation of C60 in the microwave discharge leads to a copious production of the carbon dimer molecule, C2, as evidenced by intense Swan‐band emission. Here we have investigated hydrogen–methane–argon plasmas and found that high argon fractions (≳50%) lead to intense C2 emission, indicating significant production of C2 in the plasma. In situ measurements of the substrate reflectivity were used to determine the growth rate. A correlation between the C2 emission intensity and growth rate was observed. These results prompted us to propose a scheme for diamond film growth on the (100)–(2×1): H reconstructed diamond surface with C2 as the growth species. Each surface carbon atom (bonded twice to carbons in the bulk, once to a surface carbon, creating a ‘‘dimer’’ and then forming a five‐membered ring) is terminated with hydrog...

Journal ArticleDOI
TL;DR: In this article, the Monte Carlo simulation code acat−gas has been developed in order to simulate the whole system of a planar magnetron sputtering discharge, where the atomic collisions in the cathode, which lead to sputtering and reflection, are simulated by the acat routine of acat-gas code; the thermalization of emitted atoms in the background gas within a Planar Sputtering discharge is simulated by Monte Carlo technique, where Thomas-Fermi-Morse potential is used to describe collisions between ejected atoms and background gas atoms.
Abstract: The Monte Carlo simulation code acat−gas has been developed in order to simulate the whole system of a planar magnetron sputtering discharge. The atomic collisions in the cathode, which lead to sputtering and reflection, are simulated by the acat routine of the acat−gas code; the thermalization of emitted atoms in the background gas within the a planar sputtering discharge is simulated by the Monte Carlo technique, where the Thomas–Fermi–Morse potential is used to describe collisions between ejected atoms and background gas atoms. The simulated average energy of sputtered atoms at the midpoint between the cathode and the substrate is in good agreement with experimental results. It is found that various physical quantities such as the velocity distributions of sputtered atoms and reflected atoms, the transmission rate of sputtered atoms and reflected atoms, the average energies in the background gas, and the normalized energy of arriving reflected atoms at the substrate depends strongly on the discharge vo...

Journal ArticleDOI
TL;DR: In this article, aluminum oxide coatings were reactively direct current magnetron sputtered using an arc suppression unit to stop arcing on the cathode, and the process was very controllable when the Arc suppression unit was used, and it did not produce any debilitating arcing as is commonly found with conventional reactive direct current magnetic sputtering.
Abstract: Aluminum oxide coatings were reactively direct current magnetron sputtered using an arc suppression unit to stop arcing on the cathode. The process was very controllable when the arc suppression unit was used, and it did not produce any debilitating arcing as is commonly found with conventional reactive direct current magnetron sputtering. Arc suppression is a major advancement in reactive dc magnetron sputtering technology. With the automatic feedback partial pressure control of the reactive gas, all compositions of AlOx, where 0≤x≤1.5, are possible. There are no forbidden compositions as there are with flow control of the reactive gas. All coatings were deposited with a floating substrate bias, and the color of the AlOx films ranged from metallic when there was no or a small partial pressure of oxygen during deposition to a very clear film when the oxygen partial pressure was 0.08 mTorr. The clear film was amorphous, and its average index of refraction, n, was 1.6. The Vickers hardness of the clear film...

Journal ArticleDOI
TL;DR: In this article, carbon nitride thin films were prepared using an ionized magnetron sputtering system, and an inductively coupled radio frequency (RF) plasma was generated in the region between the sputtering source (high purity graphite) and the substrate table.
Abstract: Carbon nitride thin films were prepared using an ionized magnetron sputtering system. An inductively coupled rf plasma was generated in the region between the sputtering source (high purity graphite) and the substrate table. An argon–nitrogen mixture was used as the sputtering gas. Sputtered atoms which pass through the radio frequency (rf) plasma may be ionized, and the degree of ionization depends on several processing variables, such as the gas total pressure, reactive gas partial pressure, and applied rf power. Pulsed substrate bias voltage was varied up to −500 V. Chemical bonding and composition of the deposited films were studied by infrared and Auger electron spectroscopy, respectively. An ultramicroindentation system was used to measure the hardness. Nitrogen was found to be bonded to carbon in various configurations. The dependence of the nitrogen‐to‐carbon ratio and film hardness on the deposition conditions was studied. Under optimum conditions, films with nitrogen‐to‐carbon ratio ∼0.3–0.4 and...

Journal ArticleDOI
TL;DR: In this paper, the authors used these novel alkoxysilane precursors for PECVD of SiO_2 films in an inductively coupled rf plasma reactor and described the effects of deposition time, rf power, and organosilane pressure on the films' characteristics.
Abstract: This communication describes our results using these novel alkoxysilane precursors for PECVD of SiO_2 films in an inductively coupled rf plasma reactor. The effects of deposition time, rf power, and organosilane pressure on the films’ characteristics are described.

Journal ArticleDOI
TL;DR: In this paper, Hourier transform infrared spectroscopy has been used to study the behavior of bonded hydrogen and bonded deuterium in hydrogenated amorphous silicon nitride films [a•Si:N:H(D)] that were deposited by remote plasmaenhanced chemical vapor deposition (RPECVD) and had been subjected to rapid thermal annealing (RTA) from 400 to 1200 °C.
Abstract: Fourier transform infrared spectroscopy has been used to study the behavior of bonded hydrogen and bonded deuterium in hydrogenated amorphous silicon nitride films [a‐Si:N:H(D)] that were deposited by remote plasma‐enhanced chemical vapor deposition (RPECVD) and had been subjected to rapid thermal annealing (RTA) from 400 to 1200 °C after film deposition. The amount of bonded hydrogen in the film and its distribution between Si–H and SiN–H bonding groups is correlated to the ratio (R) of the source gases: NH3 to SiH4. Chemical reaction pathways are proposed to account for bond dissociation and release of hydrogen from the films in the form of molecular H2 and NH3. As the bonded hydrogen population decreases with increasing RTA temperature, the Si–N bond population increases. This postdeposition bonding of nitrogen to silicon upon thermal release of hydrogen species is consistent with improvements in the electrical properties of RPECVD silicon nitride films after an RTA treatment at 900 °C.

Journal Article
TL;DR: In this paper, a scanning capacitance microscope (SCM) was implemented by interfacing a commercial contactmode atomic force microscope with a high-sensitivity capacitance sensor, which has promise as a next generation dopant profiling technique because the measurement is inherently two dimensional, has a potential spatial resolution limited by tip diameter of at least 20 nm, and requires no current carrying metal-semiconductor contact.
Abstract: A scanning capacitance microscope (SCM) has been implemented by interfacing a commercial contact‐mode atomic force microscope with a high‐sensitivity capacitance sensor. The SCM has promise as a next‐generation dopant‐profiling technique because the measurement is inherently two dimensional, has a potential spatial resolution limited by tip diameter of at least 20 nm, and requires no current carrying metal–semiconductor contact. Differential capacitance images have been made with the SCM of a variety of bulk‐doped samples and in the vicinity of pn junctions and homojunctions. Also, a computer code has been written that can numerically solve Poisson’s equation for a model SCM geometry by using the method of collocation of Gaussian points. Measured data and model output for similar structures are presented. How data and model output can be combined to achieve an experimental determination of dopant profile is discussed.

Journal ArticleDOI
TL;DR: In this article, a wide range Pirani gauge that is capable of measuring vacuum pressure down to 10−7 Torr reproducibly has been built, with a thermal drift as small as 5.7 μV/°C.
Abstract: As an extension of previous work in our laboratory, a wide‐range Pirani gauge that is capable of measuring vacuum pressure down to 10−7 Torr reproducibly has been built. The micromachined Pirani sensor used in the experiments has a suspended membrane that is supported by the nearly radiation‐limited, thermally insulating beam leads crossing over a V‐groove cavity. A method of partial dummy compensation, as proposed previously by Weng and Shie for eliminating the ambient drift, is proved here to be very effective with a thermal drift as small as only 5.7 μV/°C. It has also been found that a thermal‐stress‐induced piezoresistive effect, which has a profound influence on the limitation of measurement, appears in the constant‐bias operation wherein the sensor temperature rises with the reduction of gas pressure and therefore thermal conduction. This effect causes the irreproducibility of pressure measurements by the device below 10−5 Torr. In addition to its inherently higher sensitivity, a constant‐temperatu...

Journal ArticleDOI
TL;DR: In this article, the thermal stability of self-assembled monolayers of alkyl thiols, HS-(CH2)n−1−R, adsorbed on polycrystalline metal surfaces was investigated.
Abstract: Reflection‐absorption infrared spectroscopy at near grazing incidence is used to investigate the thermal stability of self‐assembled monolayers of alkyl thiols, HS–(CH2)n−1‐R, adsorbed on polycrystalline metal surfaces. The spectral features of the C–H stretching region have been carefully analyzed in the temperature range from 150 to 450 K. These features are highly sensitive to chain orientation and chain conformation. On gold, the chains are found to gradually untilt but remain largely all‐trans up to about 350 K. Above this temperature, a broad, irreversible transition to a liquidlike phase is observed, and which is characterized by a large number of gauche conformational defects. This overall behavior did not depend upon the chain length or terminal group for the systems studied. In contrast, significant differences were observed on a silver substrate.

Journal ArticleDOI
TL;DR: In this article, a nitriding apparatus based on an electron cyclotron resonance (ECR) microwave plasma source has been developed for surface modification of steel with certain advantages over conventional plasma ion ion implantation.
Abstract: Plasma source ion nitriding is a new approach for surface modification of steel with certain advantages over conventional plasma nitriding and plasma‐based nitrogen ion implantation. A nitriding apparatus based on an electron cyclotron resonance (ECR) microwave plasma source has been developed. Nitrogen ions are accelerated from the ECR microwave plasma by a low‐pulsed negative bias (typically −2 kV) which is applied directly to the workpiece, implanted, and finally diffused into the steel at elevated temperatures that are regulated up to 550 °C by an auxiliary heater. An application of plasma source ion nitriding into 1Cr18Ni9Ti austenitic stainless steel is described. The nitriding layer thicknesses are varied continuously from 0.8 to 10 μm at various process temperatures from 230 to 480 °C for a nitriding time of 4 h. A dramatic increase in microhardness has been observed. Glancing angle x‐ray diffraction has been used to determine the structural changes that occur in the nitrided surface layer.

Journal ArticleDOI
TL;DR: Energy assisted conditions for film growth are described in this paper, along with applications of the novel materials that can now be created on various substrates to improve friction, wear, corrosion resistance, and optical qualities.
Abstract: When film deposition is accompanied by bombardment by low energy (less than a few 100 eV) particles, the resulting film nucleation, growth, stress content, adhesion, density, composition, morphology, and crystal structure may be significantly altered. Current methods for providing the energy‐assisted conditions for film growth are described. Recent selected results are given demonstrating all the above features together with a discussion of the fundamental reasons for the improved film quality. Selected applications of the novel materials that can now be created on various substrates to improve friction, wear, corrosion resistance, and optical qualities are presented. The review concludes with an outline of future trends.