SiOx Capping Research Articles

Modification of boron nitride aerogels with APTES for enhanced iodine capture performance

Development of effective iodine capture materials and techniques is crucial for addressing the diverse applications of iodine and its significance in various contexts, including nuclear pollution control. This study presents the creation of a new 3-Aminopropyltriethoxysilane (APTES)-modified boron nitride (BN) aerogel designed for effective iodine capture. The internal structural units of BN aerogel, specifically the one-dimensional BN fibers, have been successfully functionalized with amine groups, resulting in the formation of an amine-rich SiOx capping layer on the surface of these fibers. The APTES modification not only establishes a stable connection within the internal BN fibers network but also imparts the material with a significant number of iodine capture sites. The resulting aerogel demonstrates an impressive iodine vapor capture capacity of 313.64 wt% at 350 K and atmospheric pressure, and up to 1028.96 mg/g in iodine/n-hexane solution, surpassing the capabilities of pure BN aerogel and most existing iodine capture materials. The excellent iodine capture performance of APTES-modified BN aerogel suggests its promising potential for future applications in iodine capture.

Application of templated vapor-liquid-solid growth to heteroepitaxy of InP on Si

Direct growth of III–V semiconductors on Si promises to combine the superior optoelectronic properties of III–Vs with the existing large-scale fabrication capabilities for Si. Vapor-liquid-solid-based growth techniques have previously been used to grow optoelectronic-quality III–Vs in polycrystalline films and various photolithography-defined features. We show that templated vapor-liquid-solid growth can produce epitaxial material when performed on crystalline substrates. In templated vapor-liquid-solid growth, the metal group-III precursor is evaporated along with a capping SiO2 layer on the crystalline substrate, then melted and converted with exposure to a vapor-phase group-V precursor. We demonstrate homoepitaxial growth of InP on InP wafers using two forms of the SiOx capping layer to confine the liquid metal: evaporated SiO2 and solgel SiOx, the latter of which is necessary for growth on Si. We then demonstrate heteroepitaxial growth of InP islands on Si substrates from both evaporated and electroplated In metals. The templated vapor-liquid-solid process provides better material utilization and growth rates than common vapor-phase techniques, with similar control and convenience, providing a path toward the large-scale fabrication of integrated optoelectronic components.

Study on the Gilbert damping of polycrystalline YIG films with different capping layers

This paper describes the effect of 5-nm thick platinum (Pt), aluminum (Al) and silicon oxide (SiOx) capping layers on the static and dynamic magnetic properties of 400-nm thick polycrystalline YIG films deposited on a Pt buffer layer. Both static and dynamic magnetic properties of Pt capped YIG film are totally different among all YIG films. Namely, the squareness of the magnetization curve for Pt capped YIG film increases, indicating that Pt capped YIG film is magnetically softer than other YIG films. Interestingly, the effective Gilbert damping parameter of Pt capped YIG films is about four times as large as those of other YIG films, and its value is approximately 9.52 × 10−4. However, the value of Gilbert damping is 2.55 × 10−4, 3.46 × 10−4 and 3.85 × 10−4 respectively for no capping, SiOx capping and Al capping samples respectively. This huge change in Gilbert damping parameter is mainly originating from the spin pumping effect, which arises at the interface of a material having strong spin orbit interaction such as Pt. Moreover, the enourmous increase in the value of effective anisotropic field and decrese in effective saturation magnetization indicates interface anisotropy is induced in Pt capped sample. These results suggest that the static and dynamic magnetic properties of YIG film can be controlled by selecting an appropriate capping layer.

Passivation Mechanisms of Atomic Layer-deposited AlOx Films and AlOx/SiOx Stack

A new passivation layer of AlOx/SiOx were prepared, in which 80 nm SiOx was prepared by spin-coating perhydropolysilazane (PHPS) and annealed at 450°C. In order to compare the passivation effect of single AlOx layers and the SiOx/AlOx stack on silicon surface, the fixed charge (Qf) in the passivated layers and chemical passivation effect were obtained by corona charge method. Fourier transform infrared spectroscopy (FTIR) and Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate the Si-H, Si-O bonds and the hydrogen profile in the passivation layer, respectively. The result reveals that the single layer of AlOx provides good field effect with a large amount of negative Qf. Furthermore, SiOx capping on AlOx have more excellent chemical passivation because of amount of H saturate the dangling bonds on the silicon surface.

Molecular beam deposition of high-density InAs quantum dots on SiOx films

InAs quantum dots (QDs) were grown on SiOx films by molecular beam deposition (MBD), and then an SiOx capping layer was deposited by rf magnetron sputtering. High arsenic pressure and As2 molecular beam flux enhanced InAs nucleation and the dot growth. Ultrahigh-density InAs QDs with 8.5 × 1011 cm−2 was obtained for As2 molecular beam of 3.0 × 10−5 Torr. The amount of InAs growth grown by As2 was about three times higher than that by As4. Photoluminescence (PL) properties depended on InAs QD structures. The vacuum transport process between InAs MBD and SiOx sputtering was effective to improve the quality of InAs QDs on a SiOx film. Furthermore, strong PL intensity was obtained from InAs QDs in a SiOx matrix, fabricated by the vacuum transport process.

Supercritical fluid-enhanced IFVD quantum well intermixing for the regrowth-free photonic integration of EAM and SOA

In this study, we propose and demonstrate the enhancement of impurity-free vacancy diffusion (IFVD) quantum well intermixing (QWI) using supercritical fluid (SCF) treatment for photonic integration. Using an InGaAsP-based multiple quantum well (MQW) template for local bandgap engineering, SCF CO2 with H2O2 on a patterned SiOx capping layer could lower the QWI temperature to get a constant wavelength blueshift. Higher oxygen concentration was found in SiOx through high diffusivities and pressures of SCF and dehydration, enabling highly activated Ga2O3 reactions for more vacancies. Additionally, different schemes of semiconductor optical amplifier (SOA)-integrated electroabsorption modulators (EAM) were fabricated. SCF treatment could realize a 9- and 6-dB improvement in extinction ratio and gain, respectively, and then high-speed 45Gb/s modulation, greatly reducing the common issue of p-type dopant (zinc) diffusion during QWI.

Ultralow Surface Recombination Velocity in Passivated InGaAs/InP Nanopillars.

The III–V semiconductor InGaAs is a key material for photonics because it provides optical emission and absorption in the 1.55 μm telecommunication wavelength window. However, InGaAs suffers from pronounced nonradiative effects associated with its surface states, which affect the performance of nanophotonic devices for optical interconnects, namely nanolasers and nanodetectors. This work reports the strong suppression of surface recombination of undoped InGaAs/InP nanostructured semiconductor pillars using a combination of ammonium sulfide, (NH4)2S, chemical treatment and silicon oxide, SiOx, coating. An 80-fold enhancement in the photoluminescence (PL) intensity of submicrometer pillars at a wavelength of 1550 nm is observed as compared with the unpassivated nanopillars. The PL decay time of ∼0.3 μm wide square nanopillars is dramatically increased from ∼100 ps to ∼25 ns after sulfur treatment and SiOx coating. The extremely long lifetimes reported here, to our knowledge the highest reported to date for undoped InGaAs nanostructures, are associated with a record-low surface recombination velocity of ∼260 cm/s. We also conclusively show that the SiOx capping layer plays an active role in the passivation. These results are crucial for the future development of high-performance nanoscale optoelectronic devices for applications in energy-efficient data optical links, single-photon sensing, and photovoltaics.

Correlation of the crystal orientation and electrical properties of silicon thin films on glass crystallized by line focus diode laser

In this work, crystallographic orientation of polycrystalline silicon films on glass formed by continuous wave diode laser crystallization was studied. Most of the grain boundaries were coincidence lattice Σ3 twin boundaries and other types of boundaries such as, Σ6, Σ9, and Σ21 were also frequently observed. The highest photoluminescence signal and mobility were observed for a grain with (100) orientation in the normal direction. X-ray diffraction results showed the highest occupancies between 41 and 70% along the (110) orientation. However, the highest occupancies changed to (100) orientation when a 100nm thick SiOx capping layer was applied. Suns-Voc measurement and photoluminescence showed that higher solar cell performance is obtained from the cell crystallized with the capping layer, which is suspected from increased occupancies of (100) orientation.

Diode laser crystallization processes of Si thin-film solar cells on glass

The crystallization of Si thin-film on glass using continuous-wave diode laser is performed. The effect of various processing parameters including laser power density and scanning speed is investigated in respect to microstructure and crystallographic orientation. Optimal laser power as per scanning speed is required in order to completely melt the entire Si film. When scan speed of 15–100 cm/min is used, large linear grains are formed along the laser scan direction. Laser scan speed over 100 cm/min forms relatively smaller grains that are titled away from the scan direction. Two diode model fitting of Suns -V oc results have shown that solar cells crystallized with scan speed over 100 cm/min are limited by grain boundary recombination (n = 2). EBSD micrograph shows that the most dominant misorientation angle is 60°. Also, there were regions containing high density of twin boundaries up to ~1.2 × 10-8 /cm2 . SiOx capping layer is found to be effective for reducing the required laser power density, as well as changing preferred orientation of the film from ⟨ 110 ⟩ to ⟨ 100 ⟩ in surface normal direction. Cracks are always formed during the crystallization process and found to be reducing solar cell performance significantly.

Fabrication of multi-wavelength In0.2Ga0.8As/GaAs multiple quantum well laser diodes by area-selective impurity-free vacancy disordering using SiOx capping layers with different stoichiometries

This work studied the implementation of multi-wavelength laser diodes on a single substrate through the position-dependent bandgap modification of the In0.2Ga0.8As/ GaAs multiple quantum wells (MQWs) by impurity-free vacancy disordering (IFVD). The position-dependent bandgap modification is achieved by performing the IFVD with SiOx capping layers with different stoichiometries. The lasing wavelength difference of about 31 nm was obtained between the ridge-waveguide laser diodes fabricated with the MQWs that had undergone the same thermal treatments using the SiOx film provided with SiH4 flow rates of 20 and 300 sccm. The device performance was not appreciably degraded in the laser diodes fabricated with the MQWs that had undergone the IFVD process .

Defect Engineering and Atomic Relocation Processes in Impurity-Free Disordered GaAs and AlGaAs

ABSTRACTImpurity-free disordering (IFD) of GaAs and AlxGa1-xAs epitaxial layers using SiOx capping in conjunction with annealing was studied by deep level transient spectroscopy (DLTS) and capacitance-voltage (C-V) measurements. Three dominant electron traps S1 (EC– 0.23 eV), S2* (EC– 0.53 eV), and S4 (EC– 0.74 eV) are created in disordered n-type GaAs. The electron emission rate of S1 is enhanced in the presence of an externally applied electric field. We propose that S1 is a defect that may involve As-clustering or a complex of arsenic interstitials, Asi, and the arsenic-antisite, AsGa. S2* is shown to be the superposition of two defects, which may be VGa-related. S4 is identified as the defect EL2. Our preliminary results indicate that the same set of defects is created in disordered n-type AlxGa1-xAs, with S1 pinned to the conduction band edge, while S2* and S4 are pinned relative to the Fermi level. In contrast to disordering in n-type GaAs, IFD of p-type GaAs results in the pronounced increase in the free carrier concentration in the near-surface region of the disordered layer. Two electrically active defects HA (EV+ 0.39 eV) and HB2 (EV+ 0.54 eV), which we have attributed to Cu- and Asi/AsGa-related levels, respectively, are also observed in the disordered p-GaAs layers. IFD causes segregation of Zn dopant atoms and Cu towards the surface of IFD samples. This atomic relocation process poses serious limitations regarding the application of IFD to the band gap engineering of doped GaAs-based heterostructures.

Impurity-free intermixing of GaAs/AlGaAs quantum wells using SiOx capping: Effect of nitrous oxide flow rate

In this work, impurity-free interdiffusion of GaAs/AlGaAs quantum wells was investigated as a function of the quality of SiOx capping layers grown by plasma-enhanced chemical vapor deposition. The quality of dielectric layers was varied by changing the nitrous oxide flow rate N (30 sccm⩽N⩽710 sccm), while maintaining a fixed silane flow rate. The pressure, substrate temperature, and rf power were also kept constant during depositions. Deposited films were characterized by Rutherford backscattering spectroscopy, spectroscopic ellipsometry, and Fourier transform infrared spectroscopy. Following rapid thermal annealing, we have observed an increase in the energy shift of quantum wells with increasing N with a maximum in the range 100 sccm<N<200 sccm. Any further increase in N resulted in a lowering in blueshift, and reached an almost constant value for N>350 sccm. The variation of energy shift with N cannot be explained by considering only the oxygen content of the SiOx layer. It is shown that the deposition rate of the capping layer plays an important role in determining the extent of quantum well intermixing. Effects related to the stress imposed by the capping layer on the GaAs/AlGaAs heterostructure and the presence of hydrogen in the capping layer are also discussed.

Effect of Stress on Impurity-Free Quantum Well Intermixing

Impurity-free interdiffusion of GaAs/AlGaAs quantum wells was investigated for SiOx capping layers grown by plasma-enhanced chemical vapor deposition. Dielectric layers were deposited for various nitrous oxide flow rates, N(30 sccm < N < 710 sccm), while maintaining a fixed silane flow rate. The oxygen content, x, of the dielectric increased monotonically with N and stoichiometric oxides were deposited above N 5 350 sccm. However, the blue shift in quantum wells did not follow a similar trend as the variation of x. Following rapid thermal annealing, the blue shift increased with the increasing N to exhibit a maximum in the range 100 sccm , N , 200 sccm. Any further increase in N resulted in a decrease in blue shift, which reached an almost constant value for N . 350 sccm. It is shown that this maximum in the blue shift is due to the stress imposed by the SiOx layer on the GaAs/AlGaAs heterostructure. © 2001 The Electrochemical Society. @DOI: 10.1149/1.1339242# All rights reserved.

Influence of SiOx Capping Layer Quality on Impurity-Free Interdiffusion in GaAs/AlGaAs Quantum Wells

AbstractWe have investigated the influence of SiOx capping layer quality on impurity-free vacancy interdiffusion in GaAs/Al0.54Ga0.46As quantum wells. Dielectric layers were deposited by plasmaenhanced chemical vapor deposition, and properties of layers were changed by varying either the flow rate of silane or deposition temperature. The extent of intermixing in our samples is discussed in terms of the 0 content and incorporation of N in capping layers, and also on their porosity. We also report on the electrically active defects which are introduced in Si02 capped and annealed n-GaAs, and relate them to the intermixing process.

Interfacial reactions of thin iron films on silicon under amorphous silicon and SiOx capping

Iron silicides were formed by annealing of iron films evaporated onto silicon wafers and capped with either amorphous silicon or SiOx thin overlayers. Pure semiconducting β-FeSi2 phase was formed at 600°C during 2 h annealing in nitrogen gas. β-FeSi2 was formed by reaction with the Si substrate and no reaction with the capping layers was observed at temperatures <800°C. After 2 h annealing at 950°C only the metallic α-FeSi2 phase was detected, and the initiation of the reaction of Fe with the amorphous silicon overlayer was observed.