Thickness Of Si3N4 Layer Research Articles

New ultrathin film heterostructure for low-e application by sputtering technique: a theoretical and experimental study

The design and optical characterization by UV–vis transmittance of ultrathin low-emissivity (low-e) windows by reactive sputtering are reported. Two heterostructures on a glass substrate were considered for the low-e windows. The first heterostructure is Si3N4/TiO2/ZnO/Ag/SnO2/Si3N4 and the second is Si3N4/Ag/Si3N4. The transmittance and reflectance of these heterostructures were simulated to determine the required thickness of each layer. The first heterostructure exhibited maximum transmittance of 85% at 550 nm, slightly higher than the one determined by simulation and less than 50% transmittance in the near-infrared region (900 nm). The second heterostructure exhibited transmittance greater than 86% at 550 nm and <50% transmittance in the near-infrared region. In addition, we found that the bandwidth and maximum position of the transmittance depend on the Si3N4 layer thickness. Specifically, the thickness of the first Si3N4 layer allows the modulation of the transmittance bandwidth and the thickness of the second Si3N4 layer allows the modulation of the maximum position. The low-e windows were protected by the deposition of an ultrathin film of NiCr alloy (Ni 80%, Cr 20%) that preserved the optical characteristics and decreased the maximum of the transmittance only by 3%.

Erratum to: Size-controlled Si quantum dots embedded in B-doped SiNx/Si3N4 superlatice for Si quantum dot solar cells

Under the condition of the fixed Si3N4 layer thickness of 1.1 nm, Si-QDs embedded in B-doped SiNx/Si3N4 multilayer thin films with various SiNx layer thickness were fabricated respectively. Si-QDs with controllable and nearly uniform size were formed in SiNx layers, and found that the optical band gap of the films can be adjusted by changing the thickness of SiNx layer. On the basis of this, the Si-QDs/c-Si heterojunction solar cells were prepared. It is found that the larger the band gap is, the higher the cell efficiency is. The best performance device is obtained with average QD size of ~3.5 nm, which has the highest efficiency of 7.05 % compared with the other two devices. This difference is caused by the difference of the spectral response of these devices.

Ultra-thin 20 nm-PECVD-Si3N4 surface passivation in T-shaped gate InAlAs/InGaAs InP-based HEMTs and its impact on DC and RF performance

Surface passivation in InP-based High Electron Mobility Transistors (HEMTs) plays an important role in reducing or eliminating their surface effects which limit both direct-current (DC) and radio-frequency (RF) performances. In the present work, effect of surface passivation was studied using an ultra-thin 20nm PECVD Si3N4 layer. In DC performance, after passivation, its maximum transconductance (gm,MAX) is increased up to 1200mS/mm. It is found that, by scaling the thickness of Si3N4 layer, the increase in Cgd after passivation can be effectively limited verified by small-signal modeling. As a result, S-parameter measurements demonstrate an increase in extracted fmax up to 450GHz after passivation. The results show that, by using an ultra-thin Si3N4 surface passivation, its RF performance can be improved in InP-based HEMTs.

Nitridation of silicon by nitrogen neutral beam

Silicon nitridation was investigated at room temperature using a nitrogen neutral beam (NB) extracted at acceleration voltages of less than 100V. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of a Si3N4 layer on a Si (100) substrate when the acceleration voltage was higher than 20V. The XPS depth profile indicated that nitrogen diffused to a depth of 36nm for acceleration voltages of 60V and higher. The thickness of the silicon nitrided layer increased with the acceleration voltages from 20V to 60V. Cross-sectional transmission electron microscopy (TEM) analysis indicated a Si3N4 layer thickness of 3.1nm was obtained at an acceleration voltage of 100V. Moreover, it was proved that the nitrided silicon layer formed by the nitrogen NB at room temperature was effective as the passivation film in the wet etching process.

Microstructure, mechanical and tribological properties of TiMoN/Si3N4 nano-multilayer films deposited by magnetron sputtering

TiMoN/Si3N4 nano-multilayer films with different Si3N4 layer thickness were synthesized using magnetron sputtering by changing the Si target current. The TiMoN/Si3N4 nano-multilayer films exhibited strong microstructure and properties dependence on the structures of Si3N4 layer. When Si3N4 layer thickness (lSi3N4) was smaller than 0.8nm, Si3N4 layers maintained crystallization state, the as-deposited TiMoN/SiNx films exhibited much higher hardness and comparable coefficient of friction (COF) than that of MoNx/SiNx films. With the further increase of lSi3N4, Si3N4 layer transformed to amorphous state, the hardness of TiMoN/Si3N4 films decreased gradually from 29.9 to 20.1GPa and COF increased from 0.55 to 0.72. It totally shows better tribological properties than TiAlSiN/Si3N4 nano-multilayer films as a result of incorporating molybdenum nitride.

Microstructure, optical properties and thermal stability of ZrB&lt;SUB&gt;2&lt;/SUB&gt; and Zr–B–N thin films as high-temperature solar selective absorbers

ZrB2 and Zr B N thin films were deposited by DC magnetron sputtering technique. The microstructure and optical properties of thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and spectrophotometer. Thin films with high selectivity (a = 9526%IsRT = 5%) were achieved by optimizing the nitrogen content of absorbing layers and thickness of antireflective layer. Thermal stability test illustrated that Zr B N thin film with high nitrogen content showed weak thermal stability due to the loose morphology of thin films. Thus, thin films with low nitrogen content and suitable thickness of Si3N4 layer can exhibit superior solar selectivity (a 91.7%lem- = 4.1%) after annealing at 500 C/60 h in air. The XRD, cross-sectional TEM and EDS results of films annealed at 500 C/100 h in air demonstrated that the solar selectivity degradation of films was due to the surface oxidation of ZrB2 layer. Moreover, the solar selectivity was still kept at high level (a = 89.05%lsRT = 10.5%) after treating in neutral salt spray for 24 h. It can be deduced that ZrB2 thin film by sputtering is a superior candidate as high-temperature solar selective absorbers.

Coherent growth and superhardness effect in VC/Si3N4 nanomultilayers

A series of VC/Si3N4 nanomultilayers have been prepared by reactive magnetron sputtering in the mixture of Ar and C2H2. Microstructure evolution and mechanical properties of multilayers with various thicknesses of Si3N4 layer have been researched. The results show that the sputtered Si3N4 doesn't react with C2H2. In VC/Si3N4 multilayers, amorphous Si3N4 is crystallized at small layer thickness (≤0.71nm) due to the template effect of VC. Correspondingly, multilayers exhibit coherent growth, and obtain significant hardness enhancement with maximum hardness of 45.9GPa. Further increasing the thickness of Si3N4 layer (≥1.45nm), Si3N4 transforms to be amorphous and blocks the coherent growth in multilayer, which leads to the gradual decrease of hardness.

Crystallization of amorphous Si3N4 and superhardness effect in HfC/Si3N4 nanomultilayers

HfC/Si3N4 nanomultilayers with various thicknesses of Si3N4 layer have been prepared by reactive magnetron sputtering. Microstructure and mechanical properties of the multilayers have been investigated. The results show that amorphous Si3N4 is forced to crystallize and grow coherently with HfC when the Si3N4 layer thickness is less than 0.95nm, correspondingly the multilayers exhibit strong columnar structure and achieve a significantly enhanced hardness with the maximum of 38.2GPa. Further increasing Si3N4 layer thickness leads to the formation of amorphous Si3N4, which blocks the coherent growth of multilayer, and thus the hardness of multilayer decreases quickly.

Electrochemical Impedance Characterization of Ultra-Thin Carbon Overcoats

Ultra-thin carbon overcoats deposited on Al2O3-TiC (AlTiC) substrates were characterized using electrochemical impedance spectroscopy. By depositing diamond-like carbon (DLC) directly on AlTiC, the polarization resistance increased to 10^7 ohm-cm2 from ~10^5 ohm-cm2 for bare AlTiC. Two adhesion layer materials were studied: Si and Si3N4. The polarization resistance of DLC/Si3N4 films was 100 times higher than that of DLC/Si. The impedance, wear and magnetic test results indicated that Si3N4 is a more suitable seed material. Comparing films with the same DLC thickness, the Si3N4 layer thickness showed no influence on the resistance. For the same Si3N4 thickness, a thicker DLC layer yielded slightly higher pore resistance. This study reveals that the thinner carbon overcoats (DLC/Si3N4 thickness = 8/12 or 12/8 Aå) provided equal, if not better, corrosion protection than the thicker films. The advantage of a thinner carbon overcoat is that it facilitates an improvement in sensitivity of the magnetic sensor.

Microstructure, Mechanical Properties and Thermal Stability of TiAlN/Si&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt; Nano-Multilayer Films Deposited by Reactive Magnetron Sputtering

A series of TiAlN/Si3N4 nano-multilayer films with various Si3N4 layer thicknesses were prepared by reactive magnetron sputtering. These multilayers were then annealed at temperatures ranging from 600 to 900°C in air for 1 hour. The composition, microstructure, and mechanical properties of the films were characterized by energy dispersive x-ray spectroscopy, x-ray diffraction, scanning electron microscopy, and nanoindentation. It reveals that under the template effect of TiAlN layers in multilayers, as-deposited amorphous Si3N4 is crystallized and grows coherently with TiAlN layers when Si3N4 layer thickness is below 0.6 nm. Correspondingly, the hardness and elastic modulus of the multilayers increase significantly. With further increase in the layer thickness, Si3N4 transforms into amorphous, resulting in a decrease of hardness and modulus. The TiAlN/Si3N4 nano-multilayers could retain their superlattice structure even up to 900°C. The small decrease in the hardness of multilayers annealed below 800°C was correlated to the release of compressive stress in multilayers. However, oxidation was found on the surface of multilayers when annealed at 800°C, which resulted in a marked decrease in the hardness of multilayers. The multilayers presented higher hardness as compared with the monolithic TiAlN film.

Induced ferromagnetism in Mn3N2 phase embedded in Mn/Si3N4 multilayers

Room temperature ferromagnetism has been obtained for different sets of Mn/Si3N4 multilayers prepared by sputtering. In order to find the most suitable conditions to stabilize the ferromagnetic ordering in this system, the evolution of the magnetic properties has been studied for films in which the Si3N4 layer thickness was maintained constant while that of the Mn layer was varied, [Mn(tm)/Si3N4(3.4 nm)]n, and conversely, in [Mn(0.7 nm)/Si3N4(tsn)]43 samples, in which the Mn layer thickness was kept constant while varying the Si3N4 layer thickness. Structural, compositional, electronic and magnetic characterizations have been performed by means of x-ray reflectometry, Rutherford backscattering spectrometry, x-ray photoemission spectroscopy, x-ray absorption, and superconducting quantum interference device for further knowledge of the magnetic-structural relationship in this system. Our results show that the peculiar magnetic behavior of these films is mainly related to the stabilization of a slightly distorted Mn3N2 phase that is induced by the Si3N4 at the interfaces. For samples with larger Mn layer thickness, metallic Mn and Mn3N2 phases coexist, which leads to a reduction of the total magnetization per Mn atom due to the presence of metallic Mn. For small Mn layer thickness (tm&amp;lt;0.86 nm), where noncontinuous Mn3N2 layers are formed, the magnetization decreases noticeably due to the superparamagnetic size limit. It has been found that the best conditions for the stabilization of the ferromagnetism in this system occur when both, the manganese-rich and the silicon nitride layers, are continuous and with similar thickness, close to 3.5 nm.

Dependence of charge trapping and tunneling on the silicon-nitride (Si3N4) thickness for tunnel barrier engineered nonvolatile memory applications

Charge trapping and tunneling characteristics of silicon-nitride (Si3N4) layer with various thicknesses were investigated for applications of tunnel barrier engineered nonvolatile memory (NVM). A critical thickness of Si3N4 layer for suppressing the charge trapping and enhancing the tunneling sensitivity of tunnel barrier were developed. Also, the charge trap centroid and charge trap density were extracted by constant current stress method. As a result, the optimization of Si3N4 thickness considerably improved the performances of NVM.

Epitaxial growth and mechanical properties of AlN/Si3N4 nanostructured multilayers

Monolithic AlN，Si3N4 films and AlN/Si3N4 multilayers with different modulation periods were prepared by reactively magnetic sputtering. The films were characterized by X-ray diffraction, high-resolution transmission electron microscopy and nanoindentation. The results showed that the crystal structure of Si3N4 layers in the multilayers and the hardness of AlN/Si3N4 multilayers depend on the thickness of Si3N4 layer. When the thickness of AlN is 4.0nm and that of Si3N4 layer is 0.4nm, Si3N4 layers grew epitaxially with AlN and form strong columnar crystals which extend over several modulation periods. A large degree of hardness enhancement of the multilayer was produced. The microstructure of Si3N4 changes from crystalline to amorphous as Si3N4 thickness increases, leading to blocking of the epitaxial growth and the superhardness effect disappears. The critical thickness of Si3N4 layers, which marks the change from crystalline to amorphous, has been calculated through thermodynamic and elastic considerations. The hardening mechanisms of AlN/Si3N4 multilayers are discussed.

Crystallization of Si3N4 and superhardness effect of ZrN/Si3N4 nano-multilayers

The crystallization behavior of Si3N4 modulation layers in the multilayers and its influences on the microstructure and mechanical properties of ZrN/Si3N4 multilayers were studied. ZrN/Si3N4 multilayers with different Si3N4 thickness were synthesized by reactive magnetic sputtering. The microstructure of the multilayers was characterized with X-ray diffraction and high-resolution transmission electron microscopy, and a nanoindentor was introduced to measure their mechanical properties. The results show that when the thickness is less than 0.9 nm, Si3N4, normally amorphous in the deposited state, could form a NaCl-type pseudocrystal structure due to the template effect of ZrN crystal layer. Crystallized Si3N4 layers and ZrN template layers grow epitaxialy into columnar crystals. Correspondingly, the hardness of the films was enhanced, showing a superhardness effect. Further increasing Si3N4 layer thickness, the coherent interfaces of the multilayers were damaged and Si3N4 layers become amorphous, accompanied by the decline in the hardness of the films.

Effects of deposition parameters on microstructure ofCrN/Si3N4 nanolayered coatings and their thermal stability

Polycrystalline CrN/Si3N4 multilayer films were deposited by using two reactive magnetron sputtering targets, Crand Si, respectively, and the as-deposited multilayer coatings were annealed at900 °C for 2–4 h in vacuum. We investigated the effects of mixed discharge gaspressure, bias voltage, substrate temperature and annealing temperatureon the microstructural and interfacial properties of polycrystallineCrN/Si3N4 multilayer films. X-ray diffraction and x-ray reflectivity measurements showedthat the layer structure of the coatings is maintained even after annealing at900 °C for 4 hwhen the Si3N4 layer thickness is 0.3 nm, which meant that with proper control of theSi3N4 thickness CrN/Si3N4 multilayer coatings had an excellent thermal stability and were potential candidates forhigh-temperature tribological applications.

Comparison of the effect of gate dielectric layer on 2DEG carrier concentration in strained AlGaN/GaN heterostructure

ABSTRACTThe effect of surface passivation on undoped AlGaN/GaN heterostructures using SiO2, Al2O3, Ta2O5 and Si3N4 as a function of layer thickness is presented. It is found that all of the oxides caused decreased 2DEG carrier concentration with increasing thickness of the respective oxide layers between the gate and AlGaN layer. On the contrary, the 2DEG carrier concentration increased strongly with increasing Si3N4 layer thickness. An elementary polarization model was used to fit the behavior for all materials and thicknesses leading to quantitative results. The fitting suggests that the effect of the oxides and Si3N4 on the 2DEG carrier concentration can be explained by the differences between them with respect to charge accumulation at the AlGaN/dielectric interface. High temperature in-situ deposited Si3N4 especially shows interesting behavior by bowing measurements as it also adds strain which increases piezoelectric polarization charge in AlGaN layer, so that increases the charge density in the 2DEG.

Application of SiO2 aerogel film for interlayer dielectric on GaAs with a barrier of Si3N4

Si3N4 film was adopted as a barrier layer for SiO2 aerogel/GaAs system. Si3N4/GaAs formed an almost chemically sharp interface and nearly maintained their chemical inertness during in-situ heating until 400 °C under ultra high vacuum condition. One micrometer thick SiO2 aerogel film was prepared on the Si3N4/GaAs system using supercritical drying procedure at 250 °C and under 1160 psi. The thickness of Si3N4 barrier layer was varied as 400, 600 and 900 Å. The dielectric constant of all SiO2 aerogel/Si3N4/GaAs system was measured as approximately 1.9 and almost no difference was observed from the changes in the thickness of Si3N4 barrier layer. The leakage current densities were measured as low as under 2×10−7 A/cm2 and these values are two orders smaller than that of SiO2 aerogel/GaAs system prepared without the introduction of Si3N4 barrier layer. All the aerogel/Si3N4/GaAs systems show ohmic conduction at low applying field and space charge limited conduction at high applying field. Furthermore, a reduced leakage current behavior was observed with increased Si3N4 layer thickness and could be explained from the electric-field depression effect due to accumulated charges in the films.

A Study on the Nitridation Mechanism of Silicon Particles

Si3N4 ceramics can be obtained by nitridation of Si powder compact accompanying a little volume change. Elucidating the nitridation mechanism of Si particle is important to control the form of Si3N4 particle. In this work, TEM analysis of the initial stage of nitridation of Si particle was conducted, and following are concluded; (a) at the initial stage of nitridation of Si particle, at temperature between 1100 to 1250°C, 10nm to 50nm thickness of Si3N4 layer is formed between the Si body and the surface oxide layer, which indicates the nitriding velocity is low. (b) the Si3N4 layer becomes thinner with decreasing the radius of Si particle. (c) The nitridation mechanism of Si particle can not be explained by linear-parabolic model, and it suggests that not only the diffusion velocity of N2 and the reaction velocity of Si and N2. (d) The volume expansion of Si3N4 shell leads a radius compressive stress and circumferential tensile stress, which are proportional to the third power of a particle radius. The radius compressive stress increases with decreasing the radius of Si particle, and it controls a nitriding velocity.