Si3N4 Buffer Layer Research Articles

Electro-optical performance of inorganic monolithic electrochromic device with a pulsed DC sputtered Li x Mg y N ion conductor

Lithium magnesium nitride (Li x Mg y N) thin films were deposited by pulsed DC reactive magnetron sputtering from a LiMg alloy target in the mixture gas of Ar and N2. The as-prepared Li x Mg y N films were amorphous. A monolithic inorganic electrochromic device (ECD) based on WO3/NiO complementary structure was fabricated using the Li x Mg y N as the ion conductor layer. The addition of a 150-nm thick Si3N4 buffer layer between Li x Mg y N and NiO made coloration and bleaching reversible and stable. Electrochemical and optical characterizations were conducted to evaluate the performance of the ECD. Electro-optical data were recorded for both 1000 chronoamperometric cycles and 1000 voltammetric cycles. Activation and degradation of the electro-optical properties of the ECD were observed.

Growth Mechanisms and Structural Properties of Lead Chalcogenide Films Grown by Pulsed Laser Deposition

Three lead chalcogenide films, PbTe, PbSe, and PbS, with a high structural quality were grown by pulsed lased deposition (PLD). The films were grown on single crystal substrates (Si, KCl, Al2O3) and on Si covered with a Si3N4 buffer layer. The Si3N4 layer latter facilitated the lead chalcogenide layer nucleation during the first growth stages and resulted in a more homogeneous surface morphology and a lower surface roughness. The surface geometry (roughness) of the films grown on Si3N4 was studied by means of the power spectral density analysis. Different growth modes, ranging from plasma plume condensation to bulk diffusion, resulting in observed film morphologies were identified. The investigations were complemented by electrical characterization of the chalcogenide films.

Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

We report the first-of-its-kind, self-organized gate-stack heterostructure of Ge-dot/SiO2/SiGe-shell on Si fabricated in a single step through the selective oxidation of a SiGe nano-patterned pillar over a Si3N4 buffer layer on a Si substrate. Process-controlled tunability of the Ge-dot size (7.5−90 nm), the SiO2 thickness (3−4 nm), and as well the SiGe-shell thickness (2−15 nm) has been demonstrated, enabling a practically-achievable core building block for Ge-based metal-oxide-semiconductor (MOS) devices. Detailed morphologies, structural, and electrical interfacial properties of the SiO2/Ge-dot and SiO2/SiGe interfaces were assessed using transmission electron microscopy, energy dispersive x-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Notably, NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors exhibit low interface trap densities of as low as 3-5x10^11 cm^-2·eV^-1 and fixed charge densities of 1-5x10^11 cm^-2, suggesting good-quality SiO2/SiGe-shell and SiO2/Ge-dot interfaces. In addition, the advantage of having single-crystalline Si1-xGex shell (x > 0.5) in a compressive stress state in our self-aligned gate-stack heterostructure has great promise for possible SiGe (or Ge) MOS nanoelectronic and nanophotonic applications.

Suppression of interface roughness between BaTiO3 film and substrate by Si3N4 buffer layer regarding aerosol deposition process

In order to decrease interface roughness, BaTiO3 films of 300 nm thickness were deposited by aerosol deposition (AD) process on Pt/Ti/SiO2/Si, Si3N4/Pt/Ti/SiO2/Si, and ZnS/Pt/Ti/SiO2/Si substrates, respectively. As a result, the Si3N4 buffer layer formed flatter interface roughness, and denser BaTiO3 film with hardness of 7.39 GPa, due to its high hardness. This dense BaTiO3 film had lower leakage current compared with the deposited films on Pt and ZnS. In addition, flat interface roughness led to the suppression of Fowler–Nordheim tunneling leakage current.

Theoretical study of graphene-silicon nitride-silicon hybrid photonic crystal waveguides for four-wave mixing enhancement

In this paper, we propose and theoretically investigate a silicon-based hybrid nonlinear photonic device with a silicon nitride (Si3N4) film sandwiched between a graphene sheet and a silicon photonic crystal waveguide (PCW). With properly designed structural parameters of the silicon PCW and the presence of Si3N4 buffer layer, enhanced interaction between the optical field and graphene can be achieved to improve four-wave mixing (FWM) process in the device. The influences of the silicon PCW and the Si3N4 buffer layer thicknesses on FWM conversion efficiency are also analyzed. Numerical simulation results show that up to 19.66 dB improvement of the FWM conversion efficiency can be obtained in the proposed device.

Beneficial Effects of ${\rm Si}_{3}{\rm N}_{4}$ Buffer/Spacer Layers on the Magnetic Properties of Exchange-Coupled PtFe/Fe Composite Films

Exchange-coupled PtFe/Fe composite films have been prepared with Si3N4 as spacer layer and buffer layer. The coercivity generally decreases with increasing thickness of the Fe layer at fixed thickness of the Si3N4 spacer layer. At fixed thickness of Fe the layer, the coercivity shows a maximum and then declines with increasing thickness of the Si3N4 spacer layer because Si3N4 layer is too thin to play a role of separation. However, the magnetic properties are significantly enhanced by a Si3N4 buffer layer, which is proposed to be due to effective prevention of diffusion between Mo and PtFe phase, as indicated by microstructure images. Fine grain sizes estimated to be about 30 nm, an enhanced coercivity and better remanence ratio indicate the beneficial effects of Si3N4 buffer layer on the magnetic properties and on the exchange-coupling of PtFe/Fe composite films.

Low transition-temperature characteristic in VOx films grown on Si3N4/Glass substrates

VOx thin films grown on a borosilicate glass substrate with a Si3N4 buffer layer by reactive ion beam sputtering with the varying substrate temperature, argon and oxygen (Ar/O2) gas mixture ratio and annealing temperature are investigated. The XRD patterns show that the films are composed of different vanadium oxides, such as V2O3, VO2, V6O13 and V2O5. The electrical resistance tests indicate that the films' phase transition temperature rises (from 29 to 35°C) as the substrate temperature increases (from 250 to 310°C). Besides, change of the Ar/O2 gas mixture ratio has a huge impact on the films' transition temperature and switching efficiency. VOx thin films fabricated with an Ar/O2 gas mixture ratio of 60:20, 60:30 and 60:40SCCM exhibit a phase transition feature at a temperature of 36, 30 and 32°C, respectively. The VOx thin films show a phase transition character at a temperature of 35, 30 and 34°C, respectively, as the annealing temperature increases from 400 to 460°C with an increment of 30°C. Additionally, the switching efficiency of sample 6 is the lowest owing to the annealing temperature which is too low to make the film oxidized completely.

Growth of High-quality GaN Thin Films on Si(111) Substrates with Silicon Nitride Buffer Layers by Using Pulsed Laser Deposition

We have grown thin films of GaN on a Si(111) substrate directly and by using a Si₃N₄ buffer layer. In an effort to analyze the surfaces of the thin...

Electrical properties of InGaN‐Si heterojunctions

AbstractThe electrical transport properties of n‐InxGa1–xN heterojunctions with Si(111) were investigated. InGaN films were grown by molecular beam epitaxy and either an AlN or Si3N4 buffer layer was used. For x in the range of 15‐45%, an ohmic junction is obtained with p‐type Si and a rectifying junction is formed with n‐type Si. The n‐InGaN/n‐Si heterojunction device functions as a solar cell. The series resistance is lower and the power conversion efficiency is higher for InGaN devices grown with an AlN buffer layer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Unusual photoluminescence properties of vertically aligned InN nanorods grown by plasma‐assisted molecular‐beam epitaxy

AbstractWe report the unusual photoluminescence (PL) properties of vertically aligned InN nanorod arrays grown on Si(111) with a Si3N4 buffer layer. The optimum growth conditions of InN nanorods are obtained by controlling the III/V ratio and the growth temperature. Structural characterization by X‐ray diffraction and scanning electron microscopy indicates that individual nanorods are wurtzite InN single crystals with the growth direction along the c‐axis. Near‐infrared PL from InN nanorods is clearly observed at room temperature. However, in comparison to the PL from InN epitaxial films, the PL from InN nanorods is significantly lower in efficiency and exhibit anomalous temperature dependence. We propose that these unusual PL properties are results of considerable structural disorder (especially for the low‐temperature grown InN nanorods) and strong surface electron accumulation effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

New Non-Volatile Memory with Magnetic Nano-Dots

We proposed a new non-volatile memory with magnetic nano-dots (MND) dispersed in an insulating film as charge retention layer. We evaluated fundamental characteristics of FePt magnetic nano-dot film which is employed in such new magnetic nano-dot memory. We successfully formed a highly ordered L10 phase face-centered tetragonal structured FePt nano-dot (< 4.2nm) films on Si3N4 (5nm)/SiO2 (10nm)/silicon substrates and SiO2(10nm)/ silicon substrate by using SAND method. The uniformity of FePt particle size is dramatically improved by introducing a Si3N4 buffer layer on SiO2/Si substrate. In addition, it is found that FePt nano-dot film formed on Si3N4 (5nm)/SiO2(10nm)/Si substrate has a large coerce-ivity of ~22 kOe at room temperature.

Properties of nitrogen-implanted p-type ZnO films grown on Si3N4/Si by radio-frequency magnetron sputtering

An nitrogen-implanted p-type ZnO film has been grown on a Si substrate buffered with Si3N4 using radio-frequency magnetron sputtering. The Si3N4 buffer layer can effectively improve film stoichiometry and reduce the formation of oxygen vacancies compared to ZnO on Si. The electrical properties of the p-type ZnO films implanted with 5×1012–1×1014 cm−2 N+ dose show a hole concentration of 5.0×1016–7.3×1017 cm−3, hole mobility of 2.51–6.02 cm2/V s, and resistivity of 10.11–15.3 Ω cm. The p-type ZnO films also showed an excellent crystallinity and a strong ultraviolet emission peak near 3.30 eV at room temperature. Moreover, as evidenced by extended x-ray absorption fine structure analysis, the local structure of the p-type ZnO films was changed due to the substitution of nitrogen ions for oxygen ions in p-type ZnO films. Our finding of p-type ZnO films grown on a Si3N4/Si substrate could provide a simple method to fabricate reproducible p-type ZnO films on silicon substrate for the development of large-scale optoelectronic integration device.

Vacuum Electron-Beam Evaporation of Fe Nanocrystals onSi3N4 Buffer Layer for carbon Nanotube Growth

Vacuum electron-beam evaporated iron nanocrystal is used for the growthof carbon nanotubes. Atomic force microscopy and Raman scatteringstudies reveal the formation of beta-iron silicide islands on baresilicon substrate after annealing at 700°C in N2 ambient. Inorder to eliminate the influence of iron-silicon interaction,Si3N4 buffer layer with the thickness of 80 nm is used.This technical route prevents effectively the formation of ironsilicide and improves the quality of the iron nanocrystals. Using theseiron nanocrystals with high density (about 7×1010/cm2) ascatalyst, high-density multiwall carbon nanotubes are synthesized onSi3N4/Si substrate.

High-performance metal–ferroelectric–insulator–semiconductor structures with a damage-free and hydrogen-free silicon–nitride buffer layer

We developed high-performance metal–ferroelectric–insulator–semiconductor (MFIS) structures with a damage-free and hydrogen-free Si3N4 buffer layer as an insulator. We fabricated Si3N4 films by nitriding Si substrates with N2 and/or atomic N radicals generated by an rf radical cell. In contrast to conventional Si3N4 films, the radical-nitride Si3N4 films showed no hysteresis or flat-band shift in the capacitance–voltage (C–V) characteristics even after high-temperature treatments, such as crystallization annealing of ferroelectric thin films deposited on the buffer Si3N4. Using this radical nitride Si3N4 as a buffer layer, we fabricated MFIS diodes with a Pt/Bi3.25La0.75Ti3O12/Si3N4/Si structure. These diodes had good hysteresis in their C–V characteristics, resulting from remnant polarization of the ferroelectric films. However, no other parasitic effects originating in charge trapping and/or detrapping were observed.

Lead zirconate titanate thin films on GaAs substrates

Thin films of the piezoceramic lead zirconate titanate (PZT) of composition Pb(Zr0.53Ti0.47)O3 have been prepared on a platinized GaAs substrate system using a propanediol based sol-gel technique. A Si3N4 buffer layer was deposited onto the GaAs by plasma-enhanced chemical vapour deposition so as to minimize Ga and As diffusion during film fabrication. Rapid thermal processing (RTP) techniques were used to thermally decompose the sol-gel layer to PZT in a further effort to avoid problems of Ga and As diffusion. Adhesion between the electrode and substrate was found to improve when an intermediate Ti layer deposited between the Pt and Si3N4 was oxidized prior to depositing the Pt layer. A crystalline PZT film was produced on the Pt/TiO2/Si3N4/GaAs by firing the sol-gel coating at 350°C for 1 min and then at 650°C for 10 s using RTP. A single deposition of precursor sol resulted in a film 0.5 μm thick. Measured average values of remanant polarization and coercive field were 14 μC cm-2 and 47 kV cm-1, respectively. The polarization value is rather low, as conventionally fired films on silicon have remanent polarization values of 20–30 μC cm-2; the lower values may be due to incomplete crystallization during RTP, but a degradation of properties due to Ga-As diffusion, despite the precautions, cannot be ruled out at this stage.

Rapid thermal N2O oxynitride on Si(100)

High-resolution x-ray photoelectron spectroscopy (XPS) in conjunction with secondary-ion-mass spectrometry was used to study the chemical nature and distribution of N in oxynitride films formed by rapid thermal N2O processes (RTPs) or conventional furnace methods. The kinetics of furnace oxide growth in N2O are slower than that in O2. During reoxidation the oxidation rate increased to that in pure O2 and the N in the SiO2–Si interface region is displaced into the bulk of the oxide. High-resolution synchrotron Si 2p core-level photoemission spectroscopy (PES) was used to study the oxide–Si(100) interface suboxide structures produced by RTP with and without the presence of N. XPS N 1s studies indicated that there are two types of N in the RTP oxynitride films. The chemical bond configuration of the first type of N is similar to that of N in Si3N4 and is mainly distributed within the first 1 nm from the interface. The second type of N is distributed mainly outside of the first 1 nm region, and the N is likely bonded to two Si and one oxygen atom. PES studies showed that Si formed suboxides with oxygen at the interface for all oxynitride films. It is found that there is no change in the Si+1 structure while there is a dramatic decrease in the Si+2 and Si+3 states with the inclusion of N in the oxide. Both the XPS and PES results are explained in terms of a strain reduction as N is incorporated in the film near the interface region, where Si3N4 functions as a buffer layer which reduces the stress caused by the large Si lattice mismatch between the bulk Si and the oxide overlayer. About 1/5 of the Si+2 and 1/3 of Si+3 atoms at the SiO2–Si interface have been replaced by the Si3N4 buffer layer at the oxynitride–Si interface.

The effect of rapid thermal N2O nitridation on the oxide/Si(100) interface structure

High-resolution x-ray photoelectron spectroscopy (XPS) was used to study the chemical nature and physical distribution of N in oxynitride films formed by rapid thermal N2O processes (RTPs). High-resolution synchrotron Si 2p core level photoemission spectroscopy (PES) was used to study the oxide/Si(100) interface suboxide structures with and without the presence of N. XPS N 1s studies indicated that there are two types of N in the RTP oxynitride films. The chemical bond configuration of the first type of N is similar to that N in Si3N4 and is mainly distributed within the first 1 nm from the interface. The second type of N is distributed mainly outside of the first 1 nm region, and the N is likely bonded to two Si and one oxygen atom. PES studies showed that Si formed suboxides with oxygen at the interface for all oxynitride films. It is found that there is no change in the Si+1 structure while there is a dramatic intensity decrease in the Si+2 and Si+3 peaks with the inclusion of N in the oxide. Both the XPS and PES results are explained in terms of a strain reduction as N is incorporated in the film near the interface region, where Si3N4 functions as a buffer layer which reduces the stress caused by the large Si ‘‘lattice’’ mismatch between the bulk Si and the oxide overlayer. About 1/5 of the Si+2 and 1/3 of Si+3 atoms at the SiO2/Si interface has been replaced by the Si3N4 buffer layer at the oxynitride/Si interface.