Oxidized Si Substrates Research Articles

Effect of Heating and Cooling Rates in Annealing for Preparation of L10-FePt Nanoparticles on Si Substrate

In order to obtain highly ordered L10-FePt nanoparticles for hard disk drive applications, the L10-phase transformation of chemically synthesized FePt nanoparticles deposited on a naturally oxidized Si substrate was investigated using rapid thermal annealing. The heating and cooling rates during annealing were changed logarithmically with a constant annealing temperature (800°C) and holding time (10 min). Almost completely ordered L10-FePt nanoparticles were confirmed by grazing incidence X-ray diffraction measurements, irrespective of the heating and cooling rates, and the amount of the silicide changed in response to both. Nearly pure L10-FePt was obtained when rapid heating (more than 780 K/min) and rapid cooling (more than 290 K/min) were applied. L10-FePt degraded into Fe3Si and PtSi when the cooling rate was lower than 7.8 K/min. Rapid heating as well as rapid cooling of FePt nanoparticles can provide a facile route for the high-throughput production of L10-FePt-based high-density magnetic recording media.

Engulfment control of platinum nanoparticles into oxidized silicon substrates for fabrication of dense solid-state nanopore arrays

We found that platinum (Pt) nanoparticles, upon annealing at high temperature of 1000 °C, are engulfed into amorphous fused-silica or thermal oxide silicon substrates. The same phenomenon was previously published for gold (Au) nanoparticles. Similar to the Au nanoparticles, the engulfed Pt nanoparticles connect to the surface of the substrates through conical nanopores, and the size of the Pt nanoparticles decreases with increasing depth of the nanopores. We explain the phenomena as driven by the formation of platinum oxide by reaction of the platinum with atmospheric oxygen, with platinum oxide evaporating to the environment. We found that the use of Pt provides much better controllability than the use of Au. Due to the high vapor pressure of platinum oxide, the engulfment of the Pt nanoparticles into oxidized silicon (SiO2) substrates is faster than of Au nanoparticles. At high temperature annealing we also find that the aggregation of Pt nanoparticles on the substrate surface is insignificant. As a result, the Pt nanoparticles are uniformly engulfed into the substrates, leading to an opportunity for patterning dense nanopore arrays. Moreover, the use of oxidized Si substrates enables us to precisely control the depth of the nanopores since the engulfment of Pt nanoparticles stops at a short distance above the SiOx/Si interface. After subsequent etching steps, a membrane with dense nanopore through-holes with diameters down to sub-30 nm is obtained. With its simple operation and high controllability, this fabrication method provides an alternative for rapid patterning of dense arrays of solid-state nanopores at low-cost.

Design Optimization of an Anisotropic Magnetoresistance Sensor for Detection of Magnetic Nanoparticles

Recent studies have shown that the magnetic field sensitivity of an anisotropic magnetoresistance (AMR) sensor using a single-layer Ni80Fe20 thin film can be considerably improved by increasing the shape anisotropy of the film. In this work, an effective approach for improving the sensitivity and reducing the magnetic coercive field as well as the thermal noise contribution in an AMR Wheatstone bridge sensor is proposed by combining multiple resistors in the series–parallel combination circuits. Four different AMR sensor designs, consisting of a single resistor, three and five resistors in series and six resistors in series–parallel connection, were fabricated by using Ta (10 nm)/Ni80Fe20 (5 nm)/Ta (10 nm) films grown on thermally oxidized Si substrates under the presence and the absence of a biasing magnetic field (900 Oe). The results showed that the sensors based on series–parallel combination gain a magnetic sensitivity (SH) 1.72 times higher than that of the sensor based on the series connection. This optimized sensor has improved the capacity of detecting various concentrations of magnetic nanoparticles with a detection limit of magnetic moments estimated to be about 0.56 μemu.

Magnetic Anisotropy and Damping Constant in CoFeB/Ir and CoFeB/Ru Systems

Co20Fe60B20 thin films of various thicknesses (3 nm $\le t_{\text {CFB}} \le 14$ nm) have been sputtered on thermally oxidized Si substrates and capped with 8 nm-thick Ir or Ru layers and then annealed at 400 °C. A vibrating sample magnetometer has been used to measure the CoFeB thickness dependence of the saturation magnetic moment per unit area in order to straightforwardly determine the magnetization at saturation and the magnetic dead layer thickness, found to be 1115 ± 50 emu/cm3 (930 ± 50 emu/cm3) and 1.53 nm (0.76 nm) for the as-deposited CoFeB/Ir (CoFeB/Ru) sytems, respectively. These values change to 1185 ± 50 emu/cm3 (1110±50 emu/cm3) and 2.93 nm (1.62 nm) for CoFeB/Ir (CoFeB/Ru) films annealed at 400 °C. Microstrip ferromagnetic resonance (MS-FMR) was used to investigate the Gilbert damping parameter and the magnetic anisotropy as a function of the CoFeB thickness. While the in-plane anisotropy field for the as-deposited films does not show a regular behavior versus the CoFeB thickness, a clear linear behavior of this field versus the reciprocal CoFeB effective thickness can be observed for the annealed samples. Moreover, the effective magnetization varies linearly with the inverse effective thickness of CoFeB due to the perpendicular interface anisotropy. This surface anisotropy constant, which was estimated to be 0.84 and 0.89 erg/cm2 for the as-deposited CoFeB films capped with Ir or Ru, respectively, reinforces the perpendicular easy axis. The corresponding anisotropy constants for the annealed Ir and Ru capped films are found to be 1.07 and 0.57 erg/cm2, respectively. Moreover, MS-FMR results revealed that the damping constant increases linearly with the reciprocal effective thickness of CoFeB, most probably due to spin pumping. The effective spin mixing conductance of the as-deposited (annealed) CoFeB/Ru and CoFeB/Ir has been estimated to be 12.93 nm−2 (22.4 nm−2) and 29.3 nm−2 (43.85 nm−2), respectively.

Large topological hall effect observed in tetragonal Mn2PtSn Heusler thin film

Tetragonal Mn-Pt-Sn Heusler compounds have been of interest because they enable magnetic antiskyrmion phases, which can potentially lead to low energy cost spintronic device applications. We report the synthesis and systematic study of the magnetic and transport properties of magnetron sputtered tetragonal Mn2PtSn thin films on the thermally oxidized Si substrates. We have observed a large topological Hall resistivity up to 0.57 μΩ cm around 150 K, which is the largest value among the Mn-based metallic materials so far. Moreover, the large topological Hall effect (THE) appears in a very wide temperature range of 10 K–300 K in a magnetic field region where the field-dependent Hall resistivity largely deviates from the magnetization. The large THE indicated here may also provide pathways towards realizing the magnetic antiskyrmions in tetragonal Mn2PtSn thin films.

Ag-Decorated Multi-Wall Carbon Nanotubes for Acetone Gas Sensing

In this study, room-temperature Acetone gas platform with enhanced sensitivity, superfast response and recovery, and good stability, using Ag nanocrystal-functionalized multiwalled carbon nanotubes. High-density carbon nanotubes (CNTs) are grown on an oxidized Si substrate by thermal chemical vapor deposition (CVD). The average length and diameter of the CNTs were about ~4.52μm and ~45nm, respectively. Ag nanoparticles were coated onto nanotube surfaces to a thickness of approximately 5nm and the CNTs thus formed could be utilized to sense acetone vapor. Functionalized CNT gas sensors exhibited better performances compared to unmodified CNTs, making them highly promising candidates for environmental air monitoring applications.

Synthesis of WO3 nanorods by thermal oxidation technique for NO2 gas sensing application

Abstracts In this work, WO3 nanorods were successfully synthesized by thermal oxidation method and further investigated for gas sensing application. For WO3 nanorods synthesis, tungsten film was deposited on oxidized Si substrate by sputtering method and subsequently subjected to thermal oxidation process at 500 °C in atmospheric environment. The synthesized nanorods were analyzed using SEM, XRD, Raman, and XPS. A chemiresistive type MEMS-based sensing device was fabricated incorporating these nanorods. The sensor was tested for different gases and VOCs over operating temperatures ranging from 75 to 300°C. It showed high selectivity towards NO2 gas over H2S, NH3, acetone, methanol, and ethanol. The excellent sensing performance and sophisticated method of synthesis make this a promising candidate for gas sensing applications.

Selective Growth of Two-Dimensional Heterostructures of Gallium Selenide on Monolayer Graphene and the Thickness Dependent p- and n-Type Nature

GaSe crystals were grown on graphene domains with few-layer graphene (FLG) grains at the centers of larger monolayer graphene (MLG) grains. We found that GaSe are selectively grown on the MLG and not on the adjacent FLG and the oxidized Si substrates. Nucleation of GaSe was preferentially occurred at the steps of FLG/MLG and MLG/SiO2 because of the presence of dangling bonds/graphene edges as supported by density function theory (DFT) calculation. We also evidenced that wrinkles on graphene were not the preferred nucleation site for GaSe if there is no dangling bond. Subsequent growth of the GaSe nuclei on MLG was favorable due to the higher migration tendency of adatoms on the MLG, as supported by DFT calculation, which promoted lateral growth of larger GaSe. The surface roughness and defects on SiO2 may also promote nucleation of GaSe on MLG. We further investigated the work functions of the GaSe/graphene heterostructures using Kelvin probe force microscopy. We have detected a unique thickness-dependent...

Enhanced Soft Magnetic Properties of [NiFe/Ta]<italic>n</italic> Laminated Films for Flux Amplification in Magnetic Sensors

The soft magnetic properties of single-layer NiFe and multilayer [NiFe/Ta] n thin films were investigated and presented in this paper. The NiFe films were prepared by RF sputtering method on thermally oxidized Si substrates at room temperature. The thickness dependence of coercivity ( $H_{c}$ ) of single-layer NiFe was revealed by the fact that the $H_{c}$ increased with the thicker films of 25, 50, 100, and 200 nm. In order to enhance the softness of the NiFe films, the non-magnetic spacer tantalum (1 nm) was introduced in the laminated structures leading to a decrease in $H_{c}$ with increase in the number of separated layers ( $n$ ). Notably, with the tantalum spacer of 1 nm at $n = 3$ , $H_{c}$ decreased dramatically from 35 down to 0.3 Oe. A minimum $H_{c}$ of 0.14 Oe was achieved at $n = 3$ and the Ta thickness of 3 nm. A possible application for the designing flux concentrator (FC) in magnetic sensor was simulated using the finite-element method. The obtained favorable results of the multilayer structures envisaged that the microfabrication of laminated [NiFe/Ta] n films would be appropriately used in magnetic sensor applications, such as the flux guide films, FC parts, and the integrated core of fluxgate sensors.

Hole conduction characteristics of cubic Ti1−xAlxN

Cubic Ti1−xAlxN (x = 0.5, 0.6) films were deposited using RF (radio frequency) magnetron sputtering and cathodic arc ion plating methods on a thermally oxidized Si substrate to evaluate the temperature dependence of their electrical characteristics by Hall measurements from 10 K to 295 K. The temperature dependence of the hole concentration and the electrical conductivity above about 200 K shows that cubic TiAlN in this study had semiconductor characteristics, indicating that the hole conduction in the valence band is dominant in a high temperature range above about 200 K. In contrast, the variable range hopping conduction is dominant in a low temperature range below about 100 K. In addition, the hole mobility of Ti0.4Al0.6N deposited by RF sputtering increased with increasing temperature above 220 K, even though the phonon scattering increases. This result shows that a disordered grain boundary between polycrystalline TiAlN acts as a barrier layer for the hole conduction.

Enhanced magnetoresistance in pulsed laser deposited stable chromium oxide thin films

Granular thin films of primarily rutile type tetragonal chromium dioxide (t-CrO2), along with a minor phase of hexagonal Cr2O3 were deposited on rutile type TiO2 layers by KrF excimer laser based pulsed laser deposition (PLD) technique using Cr2O3 targets. The TiO2 under-layer was also deposited by PLD process on oxidized Si substrates followed by annealing at 1100 °C for 10–15 min under O2 ambient. The lattice-matched interfacial TiO2 layer stabilizes the metastable Cr (IV) phase of CrO2, otherwise it readily converts into its stable phase of Cr (III) oxide, Cr2O3, under ambient conditions. Studies with X-ray diffraction (XRD) and Raman spectroscopy confirmed the stable t-CrO2 phase in the films. The microstructure in the films was studied with field emission scanning electron microscope (FESEM) and magnetic force microscope (MFM). As revealed by electrical analysis, the ferromagnetic (FM) t-CrO2 grains in conjunction with the antiferromagnetic (AFM) Cr2O3 phase in the tailored thin films effectively support an electrical transport process based on inter-granular spin-dependent tunneling (SDT) mechanism, giving rise to significantly high magnetoresistance (MR). A typical sample exhibits a markedly improved MR-value, viz., −30% at an applied field (H) of 438 kA/m at 278 K, than reported values in CrO2 thin films. Such a large MR value in the Coulomb blockade regime arises primarily not only because of the considerably suppressed spin flipping but also as a result of the highly effective SDT mechanism through an interlinked FM-AFM structure of chromium oxides in this specially engineered microstructure of the thin films. Such type of stable half-metallic thin films with low-H switching behavior is attractive for pertinent use in spintronics and magnetic sensing based applications.

Thickness-Dependent Thermal Oxidation of Ni into NiO Thin Films

We report thickness-dependent thermal oxidation in Ni (t = 10–300 nm) thin films exposed to air annealing and the resulting vibrational, magnetic and electrical properties of Ni films deposited directly on thermally oxidized Si substrate using magnetron sputtering technique at ambient temperature. As-deposited Ni films exhibit face-centred cubic structure with fine crystals and large lattice constant (aNi) at lower t ( 50 due to formation of NiO. The relative fraction of Ni and NiO in annealed films up to 400 ∘C strongly depends on t. Annealing Ni films at 500 ∘C results into complete oxidation of Ni into granular-type NiO. X-ray reflectivity studies reveal that oxidation process occurs from surface of the films converting Ni into NiO possibly through layer by layer process, which is subtle to t. Raman spectra show that intensity ratio between one-phonon longitudinal optical (LO) and two-phonon LO bands decreases and intensity of two-magnon band increases with increasing t for films annealed at particular TA. This confirms the growth of NiO not only with increasing TA, but also with t. As-deposited films exhibit ferromagnetism at room temperature. The presence of Ni and NiO in annealed films implies coexistence of ferromagnetic and antiferromagnetic interactions, leading to tunable exchange bias (HE), whose magnitude strongly depends on the ratio between Ni and NiO. Electrical resistance (R) of the as-deposited Ni films decreases with increasing t and follows the Namba’s model. Upon annealing, R increases largely due to oxidation of Ni. The observed results are explained on the basis of thickness dependent thermal oxidation process with increasing TA.

Comparative study of sculptured metallic thin films deposited by oblique angle deposition at different temperatures.

Metals with a wide range of melting points are deposited by electron beam evaporation under oblique deposition geometry on thermally oxidized Si substrates. During deposition the sample holder is cooled down to 77 K. It is observed that all obliquely deposited metals grow as tilted, high aspect ratio columns and hence with a similar morphology. A comparison of such columns with those deposited at room temperature (300 K) reveals that shadowing dominates the growth process for columns deposited at 77 K, while the impact of surface diffusion is significantly increased at elevated substrate temperatures. Furthermore, it is discussed how the incidence angle of the incoming particle flux and the substrate temperature affect the columnar tilt angles and the porosity of the sculptured thin films. Exemplarily for tilted Al columns deposited at 77 K and at 300 K, in-plane pole figure measurements are carried out. A tendency to form a biaxial texture as well as a change in the crystalline structure depending on the substrate temperature is found for those films.

Tunable magnetic and transport properties of Mn3Ga thin films on Ta/Ru seed layer

Hexagonal D019-type Mn3Z alloys that possess large anomalous and topological-like Hall effects have attracted much attention due to their great potential in antiferromagnetic spintronic devices. Herein, we report the preparation of Mn3Ga films in both tetragonal and hexagonal phases with a tuned Ta/Ru seed layer on a thermally oxidized Si substrate. Large coercivity together with large anomalous Hall resistivity is found in the Ta-only sample with a mixed tetragonal phase. By increasing the thickness of the Ru layer, the tetragonal phase gradually disappears and a relatively pure hexagonal phase is obtained in the Ta(5)/Ru(30) buffered sample. Further magnetic and transport measurements revealed that the anomalous Hall conductivity nearly vanishes in the pure hexagonal sample, while an abnormal asymmetric hump structure emerges in the low field region. The extracted additional Hall term is robust in a large temperature range and presents a sign reversal above 200 K. The abnormal Hall properties are proposed to be closely related to the frustrated spin structure of D019 Mn3Ga.

Experimental study of a SINIS detector response time at 350 GHz signal frequency

Response time constant of a SINIS bolometer integrated in an annular ring antenna was measured at a bath temperature of 100 mK. Samples comprising superconducting aluminium electrodes and normal-metal Al/Fe strip connected to electrodes via tunnel junctions were fabricated on oxidized Si substrate using shadow evaporation. The bolometer was illuminated by a fast black-body radiation source through a band-pass filter centered at 350 GHz with a passband of 7 GHz. Radiation source is a thin NiCr film on sapphire substrate. For rectangular 10÷100 μs current pulse the radiation front edge was rather sharp due to low thermal capacitance of NiCr film and low thermal conductivity of substrate at temperatures in the range 1-4 K. The rise time of the response was ~1-10 μs. This time presumably is limited by technical reasons: high dynamic resistance of series array of bolometers and capacitance of a long twisted pair wiring from SINIS bolometer to a room-temperature amplifier.

Ammonia gas sensors with Au-decorated carbon nanotubes

In this study, high-density carbon nanotubes (CNTs) are grown on an oxidized Si substrate by thermal chemical vapor deposition (CVD). CNTs were synthesized by thermal CVD at 700 °C in a C2H2 atmosphere and used to fabricate a gas sensing-device. The average length and diameter of the CNTs were about ~ 4.52 μm and ~ 45 nm, respectively. Au nanoparticles were coated onto nanotube surfaces to a thickness of approximately 5 nm and the CNTs thus formed could be utilized to sense acetone vapor. In 800 ppm ammonia (NH3) vapor at room temperature, the adsorption of Au nanoparticles increased the sensitivities of the device to these species from 1.11, 1.54, 2.03, 2.44 and 2.74%, respectively.

Tuning Magnetic Properties of Thick CoFeB Film by Interlayer Coupling in Trilayer Structured Thin Films

This study deals with tuning magnetic properties of a thick amorphous (a-)Co20Fe60B20 (CoFeB262) film by using interlayer magnetic coupling in trilayer structured films of [CoFeB262 (100 nm)/[Cr,Ta (x nm)]/CoFeB262 (y nm)] with y=2-50, xCr=0.75, 2 and xTa=1, 4. All the films are deposited directly on thermally oxidized Si substrate at ambient temperature using magnetron sputtering. The as-deposited a-CoFeB262 (100 nm) film exhibits magnetic stripe domain and transcritical hysteresis loop due to large effective magnetic anisotropy caused by stress induced during deposition of the films. On the other hand, the shape of magnetic hysteresis (M-H) loops in trilayer films transforms from transcritical to rectangular shaped one with enhanced remanence ratio (MR/MS) of ≥ 75% and single magnetization reversal behavior. This effectively reduces coercivity (HC) and field required to saturate magnetization (HS) in trilayer films. However, the changes in the loop shape and reductions in HC and HS depend strongly on x and y. Magnetic domain images obtained using Kerr microscopy in trilayer films show a rapid switching of large-sized domains along easy-axis and weak ripple domains along hard-axis. In addition, the magnetization reversal behavior along the hard-axis strongly depends on x(Cr,Ta). M-H loops obtained at different temperatures between 30 K and 300 K reveal no change in loop shape for trilayer films with small x and y, while the disappearance of shearing and formation of additional steps at low temperatures are observed for films with large x and y. The observed results are explained on the basis of change in interlayer coupling between CoFeB262 layers with x, y and temperature. Furthermore, these results clearly confirm that the magnetic properties of thick CoFeB262 film with stripe domain can easily be tuned into in-plane magnetization by this simple trilayer structured thin films.

Thickness Dependent Surface Topography, Magnetic Properties and Magnetic Domain Structure of Amorphous FeTaC Thin Films

We report systematic investigation of thickness dependent surface topography, magnetic properties and magnetic domain structures of amorphous Fe80Ta8C12 (x nm) films with x=5–100 nm. All the as-deposited films fabricated directly on thermally oxidized Si substrate at ambient temperature using magnetron sputtering technique exhibit amorphous structure. The structural studies reveal that island-like structure in ultra-thin films transforms into continuous one with increasing x>10. In addition, the average surface roughness increases with increasing x, but without any systematic dependency on x. Room temperature magnetic properties illustrate that the paramagnetic nature observed for films with x 97%), low coercivity (HC 3.5 kA/m) and HS (>40 kA/m) and reduced MR/MS (<45%). The magnetic domain studies not only reveal that the domains change from in-plane magnetization to dense stripe domain pattern with increasing x due to enhancement of effective magnetic anisotropy caused by stress quenched in during deposition, but also confirm that films with 12<x<40 exhibit in-plane magnetization with uniaxial anisotropy. High temperature thermomagnetization reveal a clear magnetic phase transition from ferromagnetic to paramagnetic state at relatively higher temperature of about 530 K. The observed results are elucidated on the basis of enhanced effective magnetic anisotropy, change in the magnetic domain structure and magnetic disorder with increasing FeTaC film thickness.

Demonstration of four-state memory structure with perpendicular magnetic anisotropy by spin-orbit torque

Current, instead of magnetic field, induced magnetization switching is very important for future spintronics in information storage or/and information processing. As one of the effective current-induced magnetization methods, spin-orbit torque (SOT) has aroused considerable interest because it has low-power consumption and can improve the device endurance. Normal metal (NM)/ferromagnetic metal (FM) are the common materials used for SOTs, where the NM denotes the materials with strong spin-orbit coupling such as Pt, Ta, W, etc. Owing to the spin Hall effect, the in-plane current in NM layer can be converted into a vertical spin current that exerts torques on the adjacent FM layers. Spin current can also come from the NM/FM interface charge-spin conversion due to interfacial asymmetry, exerting torques on the adjacent FM layers. Materials with in-plane and perpendicular magnetic anisotropy are used to study the SOT-induced magnetization switching. Compared with the memories using the in-plane ferromagnetic films, the magnetic memories using NM/FM multilayers with perpendicular magnetic anisotropy can have much high integration density. Currently the used information storage was based on the two-state memory cell. Owing to more than two states contained in one memory cell, multiple states memory manipulated by electric current could further benefit the higher-density memory. In this paper, a four-state memory unit is demonstrated by the influence of TaOx buffer layer on the magnetic anisotropy of Pt/Co/Pt multilayers. The memory unit consists of two regions. One is directly deposited on thermal oxide Si substrate[Pt(3 nm)/Co(0.47 nm)/Pt(1.5 nm)] and the other has a buffer layer of TaOx[TaOx(0.3 nm)/Pt(3 nm)/Co(0.47 nm)/Pt(1.5 nm)], thus leading to the difference in magnetic property between these two regions. According to the Z axis magnetic hysteresis loops of two regions, measured by polar magneto-optical Kerr effect, the coercivity of the region with TaOx is obtained to be 23 Oe and that without TaOx is 11 Oe. At the junction between two regions, the magnetic hysteresis loop shows the superposition of hysteresis loops of two regions, resulting in switching four times as the magnetic field changes. Under a fixed magnetic field along the current direction, the magnetization orientation of region with TaOx and that of region without TaOx are switched by spin-orbit torques with threshold currents of 5 mA and 1.5 mA respectively. The switching direction can be changed as the in-plane magnetic field changes to the opposite direction, which is one of the typical features of SOTs-induced magnetization switching. At the junction between two regions, through applying different-form current pulses to one conductive channel of the device, the magnetic state of the memory cell can be switched between four clear states. This kind of structure provides a new idea to design SOT multi-state memory devices.

Hydrogen production via methanol oxidation on platinum oxide thin film catalyst: Influence of methanol-to-oxygen ratio

Platinum oxide (PtOx) thin films deposited by means of radio frequency (rf) magnetron sputtering on oxidized Si substrate were investigated under realistic conditions as efficient catalysts promoting oxidation of methanol to produce hydrogen. The main focus was given to the role of reactant mixture (methanol + oxygen) composition at different surface temperatures. Freshly deposited PtOx changes its chemical state and morphology during the initial reaction leading to strongly corrugated metallic Pt layer with small amounts of stable Pt2+ cations providing a crucial ingredient for its specific catalytic properties. With growing temperature or methanol-to-oxygen molar ratio the reaction selectivity of such catalyst generally shifts from pathways producing water to those generating hydrogen. The efficiency for a given reaction route can be thus maximized via independent tuning of the fuel-oxygen ratio and surface temperature. The most intensive hydrogen evolution with the lowest relative amount of CO by-product (but relatively high abundance of methanolic residuals) was achieved with mildly oxygen lean feed above 500 K. The highest selectivity for partial oxidation of methanol pathway (>80%) can be, on the other hand, obtained with stoichiometric or oxygen rich mixture.