RESUMEN

The modification of nanodiamond (ND) surfaces has significant applications in sensing devices, drug delivery, bioimaging, and tissue engineering. Precise control of the diamond phase composition and bond configurations during ND processing and surface finalization is crucial. In this study, we conducted a comparative analysis of the graphitization process in various types of hydrogenated NDs, considering differences in ND size and quality. We prepared three types of hydrogenated NDs: high-pressure high-temperature NDs (HPHT ND-H; 0-30 nm), conventional detonation nanodiamonds (DND-H; ~5 nm), and size- and nitrogen-reduced hydrogenated nanodiamonds (snr-DND-H; 2-3 nm). The samples underwent annealing in an ultra-high vacuum and sputtering by Ar cluster ion beam (ArCIB). Samples were investigated by in situ X-ray photoelectron spectroscopy (XPS), in situ ultraviolet photoelectron spectroscopy (UPS), and Raman spectroscopy (RS). Our investigation revealed that the graphitization temperature of NDs ranges from 600 °C to 700 °C and depends on the size and crystallinity of the NDs. Smaller DND particles with a high density of defects exhibit a lower graphitization temperature. We revealed a constant energy difference of 271.3 eV between the sp-peak in the valence band spectra (at around 13.7 eV) and the sp3 component in the C 1s core level spectra (at 285.0 eV). The identification of this energy difference helps in calibrating charge shifts and serves the unambiguous identification of the sp3 bond contribution in the C 1s spectra obtained from ND samples. Results were validated through reference measurements on hydrogenated single crystal C(111)-H and highly-ordered pyrolytic graphite (HOPG).

RESUMEN

Following defocused ion beam sputtering, large area highly corrugated and faceted nanoripples are formed on calcite (10.4) faces in a self-organized fashion. High resolution atomic force microscopy (AFM) imaging reveals that calcite ripples are defined by facets with highly kinked (11.0) and (21¯.12) terminations.In situAFM imaging during the exposure of such modified calcite surfaces to PbCl2aqueous solution reveals that the nanostructured calcite surface promotes the uptake of Pb. In addition, we observed the progressive smoothing of the highly reactive calcite facet terminations and the formation of Pb-bearing precipitates elongated in registry with the underlying nanopattern. By SEM-EDS analysis we quantified a remarkable 500% increase of the Pb uptake rate, up to 0.5 atomic weight % per hour, on the nanorippled calcite in comparison to its freshly cleaved (10.4) surfaces. These results suggest that nanostructurated calcite surfaces can be used for developing future systems for lead sequestration from polluted waters.

Asunto(s)

Carbonato de Calcio , Nanoestructuras , Plomo , Agua , Microscopía de Fuerza Atómica/métodos

RESUMEN

Tungsten disulfide (WS2) was prepared from W metal and WO3 by ion beam sputtering and sulfurization in a different number of layers, including monolayer, bilayer, six-layer, and nine-layer. To obtain better crystallinity, the nine-layer of WS2 was also prepared from W metal and sulfurized in a furnace at different temperatures (800, 850, 900, and 950 °C). X-ray diffraction revealed that WS2 has a 2-H crystal structure and the crystallinity improved with increasing sulfurization temperature, while the crystallinity of WS2 sulfurized from WO3 (WS2-WO3) is better than that sulfurized from W-metal (WS2-W). Raman spectra show that the full-width at half maximum (FWHM) of WS2-WO3 is narrower than that of WS2-W. We demonstrate that high-quality monocrystalline WS2 thin films can be prepared at wafer scale by sulfurization of WO3. The photoluminescence of the WS2 monolayer is strongly enhanced and centered at 1.98 eV. The transmittance of the WS2 monolayer exceeds 80%, and the measured band gap is 1.9 eV, as shown by ultraviolet-visible-infrared spectroscopy.

RESUMEN

Spin pumping has been considered a powerful tool to manipulate the spin current in a ferromagnetic/nonmagnetic (FM/NM) system, where the NM part exhibits large spin-orbit coupling (SOC). In this work, the spin pumping in ß-W/Interlayer (IL)/Co2FeAl (CFA) heterostructures grown on Si(100) is systematically investigated with different ILs in which SOC strength ranges from weak to strong. We first measure the spin pumping through the enhancement of effective damping in CFA by varying the thickness of ß-W. The damping enhancement in the bilayer of ß-W/CFA (without IL) is found to be ∼50% larger than the Gilbert damping in a single CFA layer with a spin diffusion length and spin mixing conductance of 2.12 ± 0.27 nm and 13.17 ± 0.34 nm-2, respectively. Further, the ILs of different SOC strengths such as Al, Mg, Mo, and Ta were inserted at the ß-W/CFA interface to probe their impact on damping in ß-W/ILs/CFA. The effective damping reduced to 8% and 20% for Al and Mg, respectively, whereas it increased to 66% and 75% with ILs of Mo and Ta, respectively, compared to the ß-W/CFA heterostructure. Thus, in the presence of ILs with weak SOC, the spin pumping at the ß-W/CFA interface is suppressed, while for the high SOC ILs effective damping increased significantly from its original value of ß-W/CFA bilayer using a thin IL. This is further confirmed by performing inverse spin Hall effect measurements. In summary, the transfer of spin angular momentum can be significantly enhanced by choosing a proper ultrathin interface layer. Our study provides a tool to increase the spin current production by inserting an appropriate thin interlayer which is useful in modifying the heterostructure for efficient performance in spintronics devices.

RESUMEN

The synergistic effect of high-quality NiOxhole transport layers (HTLs) deposited by ion beam sputtering on ITO substrates and the Ti3C2TxMXene doping of CH3NH3PbI3(MAPI) perovskite layers is investigated in order to improve the power conversion efficiency (PCE) of p-i-n perovskite solar cells (PSCs). The 18 nm thick NiOxlayers are pinhole-free and exhibit large-scale homogeneous surface morphology as revealed by the atomic force microscopy (AFM). The grazing-incidence x-ray diffraction showed a 0.75% expansion of the face-centered cubic lattice, suggesting an excess of oxygen as is typical for non-stoichiometric NiOx. The HTLs were used to fabricate the PSCs with MXene-doped MAPI layers. A PSC with undoped MAPI layer served as a control. The size of MAPI polycrystalline grains increased from 430 ± 80 nm to 620 ± 190 nm on the doping, as revealed by AFM. The 0.15 wt% MXene doping showed a 14.3% enhancement in PCE as compared to the PSC with undoped MAPI. The energy-resolved electrochemical impedance spectroscopy revealed one order of magnitude higher density of defect states in the band gap of MXene-doped MAPI layer, which eliminated beneficial effect of reduced total area of larger MAPI grain boundaries, decreasing short-circuit current. The PCE improvement is attributed to a decrease of the work function from -5.26 eV to -5.32 eV on the MXene doping, which increased open-circuit voltage and fill factor.

RESUMEN

Gallium oxide is an ultra-wide band gap semiconductor (Eg > 4.4 eV), best suited intrinsically for the fabrication of solar-blind photodetectors. Apart from its crystalline phases, amorphous Ga2O3 based solar-blind photodetector offer simple and facile growth without the hassle of lattice matching and high temperatures for growth and annealing. However, they often suffer from long response times which hinders any practical use. Herein, we report a simple and cost-effective method to enhance the device performance of amorphous gallium oxide thin film photodetector by nanopatterning the surface using a broad and low energy Ar+ ion beam. The ripples formed on the surface of gallium oxide thin film lead to the formation of anisotropic conduction channels along with an increase in the surface defects. The defects introduced in the system act as recombination centers for the charge carriers bringing about a reduction in the decay time of the devices, even at zero-bias. The fall time of the rippled devices, therefore, reduces, making the devices faster by more than 15 times. This approach of surface modification of gallium oxide provides a one-step, low cost method to enhance the device performance of amorphous thin films which can help in the realization of next-generation optoelectronics.

RESUMEN

Surface nanopatterning induced by ion beam irradiation (IBI) has emerged as an effective nanostructuring technique since it induces patterns on large areas of a wide variety of materials, in short time, and at low cost. Nowadays, two main subfields can be distinguished within IBI nanopatterning depending on the irrelevant or relevant role played by the surface composition. In this review, we give an up-dated account of the progress reached when surface composition plays a relevant role, with a main focus on IBI surface patterning with simultaneous co-deposition of foreign atoms. In addition, we also review the advances in IBI of compound surfaces as well as IBI systems where the ion employed is not a noble gas species. In particular, for the IBI with concurrent metal co-deposition, we detail the chronological evolution of these studies because it helps us to clarify some contradictory early reports. We describe the main patterns obtained with this technique as a function of the foreign atom deposition pathway, also focusing in those systematic studies that have contributed to identify the main mechanisms leading to the surface pattern formation and development. Likewise, we explain the main theoretical models aimed at describing these nanopattern formation processes. Finally, we address two main special features of the patterns induced by this technique, namely, the enhanced pattern ordering and the possibility to produce both morphological and chemical patterns.

RESUMEN

The investigation of chemical and optoelectronic properties of halide perovskite layers and associated interfaces is crucial to harness the full potential of perovskite solar cells. Depth-profiling photoemission spectroscopy is a primary tool to study the chemical properties of halide perovskite layers at different scales from the surface to the bulk. The technique employs ionic argon beam thinning that provides accurate layer thicknesses. However, there is an urgent need to corroborate the reliability of data on chemical properties of halide perovskite thin films to better assess their stability. The present study addresses the question of the Ar+ sputtering thinning on the surface chemical composition and the optoelectronic properties of the triple-cation mixed-halide perovskite by combining X-ray photoemission spectroscopy (XPS) and photoluminescence (PL) spectroscopy. First, XPS profiling is performed by Ar+ beam sputtering on a half-cell: glass/FTO/c-TiO2/perovskite. The resulting profiles show a very homogeneous and reproducible element distribution until near the buried interface; therefore, the layer is considered as quasihomogeneous all over its thickness, and the sputtering process is stable. Second, we evaluated a set of thinned perovskite layers representative of selected steps along the profile by means of PL imaging optical measurements in both steady-state and transient regimes to assess possible perturbation of the optical properties from the surface to bulk. Obtained PL spectra inside the resulting craters show no peak shift nor phase segregation. Accordingly, the transient PL measurements do not reveal any changes of the surface recombination rate in the sputtered areas. This demonstrates that there is no cumulative effect of sputtering nor drastic chemical and optoelectronic modifications, validating the determination of the in-depth composition of the perovskite layer. Combining XPS profiling with PL characterization can be a precise tool to be applied for an extensive study of the multiple layers and mixed organic/inorganic interfaces of photovoltaic devices.

RESUMEN

Thin films of beryllium and gold that are several tens of nanometers thick were obtained, for the first time, on silicon and quartz substrates by the ion-beam method with tenfold alternation of deposition and partial sputtering of the nanosized metal layer. Scanning electron and atomic force microscopy indicate the predominant lateral growth of nanosized metal layers along the substrate surface. Optical spectra indicate the suppression of the localized plasmon resonance. The growth of the film occurs under the influence of the high-energy component of the sputtered metal atoms' flux. The main role in the formation of the nanosized metal film is played by the processes of the elastic collision of incident metal atoms with the atoms of a substrate and a growing metal film. Metal films that are obtained by the tenfold application of the deposition-sputtering of a nanoscale metal layer are characterized by stronger adhesion to the substrate and have better morphological, electrical, and optical characteristics than those that are obtained by means of direct single deposition.

RESUMEN

Zirconia- and hafnia-based thin films have attracted tremendous attention in the past decade because of their unexpected ferroelectric behavior at the nanoscale, which enables the downscaling of ferroelectric devices. The present work reports an unprecedented ferroelectric rhombohedral phase of ZrO2 that can be achieved in thin films grown directly on (111)-Nb:SrTiO3 substrates by ion-beam sputtering. Structural and ferroelectric characterizations reveal (111)-oriented ZrO2 films under epitaxial compressive strain exhibiting switchable ferroelectric polarization of about 20.2 µC/cm2 with a coercive field of 1.5 MV/cm. Moreover, the time-dependent polarization reversal characteristics of Nb:SrTiO3/ZrO2/Au film capacitors exhibit typical bell-shaped curve features associated with the ferroelectric domain reversal and agree well with the nucleation limited switching (NLS) model. The polarization-electric field hysteresis loops point to an activation field comparable to the coercive field. Interestingly, the studied films show ferroelectric behavior per se, without the need to apply the wake-up cycle found in the orthorhombic phase of ZrO2. Overall, the rhombohedral ferroelectric ZrO2 films present technological advantages over the previously studied zirconia- and hafnia-based thin films and may be attractive for nanoscale ferroelectric devices.

RESUMEN

Aluminum optics are widely used in modern optical systems because of their high specific stiffness and high reflectance. With the applied optical frequency band moving to visible, traditional processing technology cannot meet the processing precision. Ion beam sputtering (IBS) provides a highly deterministic technology for high-precision aluminum optics fabrication. However, the surface quality is deteriorated after IBS. The interaction between the bombard atoms and the surface morphology evolution mechanism are not clear, and systematic research is needed. Thus, in this paper, the IBS process for single crystal aluminum with different crystallographic orientations are studied by the molecular dynamics method. The ion beam sputter process is firstly demonstrated. Then, the variation of sputter yield of the three crystal faces is analyzed. The sputter yield difference of different crystal surfaces causes the appearance of the relief structure. Then, the gravel structure generates on the single crystal surfaces and dominates the morphology evolution. The state of the atom diffusion of the specific crystal surfaces will determine the form of the gravel structure. Furthermore, the form and distribution of subsurface damage and stress distribution of three different crystal surfaces are analyzed. Although there are great differences in defect distribution, no stress concentration was found in three workpieces, which verifies that the ion beam sputter is a stress-free machining method. The process of IBS and the mechanism of morphology evolution of aluminum are revealed. The regularity and mechanism will provide a guidance for the application of IBS in aluminum optics manufacture fields.

RESUMEN

This work reports the self-organization of dimple nanostructures on a polyethylene naphthalate (PEN) surface where an Ar ion beam was irradiated at an ion energy of 600 eV. The peak-to-peak roughness and diameter of dimple nanostructures were 29.1~53.4 nm and 63.4~77.6 nm, respectively. The electron energy loss spectrum at the peaks and troughs of dimples showed similar C=C, C=O, and O=CH bonding statuses. In addition, wide-angle X-ray scattering showed that Ar ion beam irradiation did not induce crystallization of the PEN surface. That meant that the self-organization on the PEN surface could be due to the ion-induced surface instability of the amorphous layer and not due to the partial crystallinity differences of the peaks and valleys. A nonlinear continuum model described surface instability due to Ar ion-induced sputtering. The Kuramoto-Sivashinsky model reproduced the dimple morphologies numerically, which was similar to the experimentally observed dimple patterns. This preliminary validation showed the possibility that the continuum equation used for metal and semiconductor surfaces could be applied to polymer surfaces where ion beam sputtering occurred.

RESUMEN

Recently, the deep ultraviolet (DUV) photodetectors fabricated from two-dimensional (2D) hexagonal boron nitride (h-BN) layers have emerged as a hot research topic. However, the existing studies show that the h-BN-based photodetectors have relatively poor performance. In this work, C doping is utilized to modulate the properties of h-BN and improve the performance of the h-BN-based photodetectors. We synthesized the h-BN atomic layers with various C concentrations varying from 0 to 10.2 atom % by ion beam sputtering deposition through controlling the sputtering atmosphere. The h-BN phase remains stable when a small amount of C is incorporated into h-BN, whereas the introduction of a large amount of C impurities leads to the rapidly deteriorated crystallinity of h-BN. Furthermore, the DUV photodetectors based on C-doped h-BN layers were fabricated, and the h-BN-based photodetector with 7.5 atom % C exhibits the best performance with a responsivity of 9.2 mA·W-1, which is significantly higher than that of the intrinsic h-BN device. This work demonstrates that the C doping is a feasible and effective method for improving the performance of h-BN photodetectors.

RESUMEN

Atomically thin hexagonal boron nitride (h-BN) is gaining significant attention for many applications such as a dielectric layer or substrate for graphene-based devices. For these applications, synthesis of high-quality and large-area h-BN layers with few defects is strongly desirable. In this work, the aligned growth of millimeter-size single-crystal h-BN domains on epitaxial Ni (111)/sapphire substrates by ion beam sputtering deposition is demonstrated. Under the optimized growth conditions, single-crystal h-BN domains up to 0.6 mm in edge length are obtained, the largest reported to date. The formation of large-size h-BN domains results mainly from the reduced Ni-grain boundaries and the improved crystallinity of Ni film. Furthermore, the h-BN domains show well-aligned orientation and excellent dielectric properties. In addition, the sapphire substrates can be repeatedly used with almost no limit. This work provides an effective approach for synthesizing large-scale high-quality h-BN layers for electronic applications.

RESUMEN

The features of InAs quantum dots obtained on GaAs(001) single-crystal substrates by ion-beam sputtering were investigated. It has been shown that in the range of ion energies of 150 to 200 eV at a temperature of 500 °C and a beam current of 120 µA InAs quantum dots with average dimensions below 15 nm and a surface density of 1011 cm-2 are formed. The technique of controlled doping of InAs/GaAs nanostructures using a SnTe solid-state source was proposed. It has been established that a maximum donor concentration of 8.7·1018 cm-3 in the GaAs spacer layer is reached at an evaporation temperature of 415 °Ð¡. At the same time, impurity accumulation in the growth direction was observed. We have shown that increasing the impurity doping of the GaAs barrier layer increases the intensity of photoluminescence peaks of the ground state and the first excited state of the InAs quantum dots.

RESUMEN

In the present state of the art, ion beam sputtering is used to produce low-loss dielectric optics. During the manufacturing of a dielectric layer stack, the deposition material must be changed, which requires rapid mechanical movement of vacuum components. These mechanical components can be regarded as a risk factor for contamination during the coating process, which limits the quality of high-end laser components. To minimize the particle contamination, we present a novel deposition concept that does not require movable components to change the coating material during the coating process. A magnetic field guiding technique has been developed, which enables the tuning of the refractive index in the layer structure by sputtering mixtures with varying compositions of two materials using a single-ion source. The versatility of this new concept is demonstrated for a high-reflection mirror.

RESUMEN

A uniform graphene nanodots inlaid porous gold electrode was prepared via ion beam sputtering deposition (IBSD) and mild corrosion chemistry. HRTEM, SEM, AFM and XPS analyses revealed the successful fabrication of graphene nanodots inlaid porous gold electrode. The as-prepared porous electrode was used as π-orbital-rich drug loading platform to fabricate an electrochemically controlled drug release system with high performance. π-orbital-rich drugs with amino mioety, like doxorubicin (DOX) and tetracycline (TC), were loaded into the graphene nanodots inlaid porous gold electrode via non-covalent π-π stacking interaction. The amino groups in DOX and TC can be easily protonated at acidic medium to become positively-charged NH3(+), which allow these drug molecules to be desorbed from the porous electrode surface via electrostatic repulsion when positive potential is applied at the electrode. The drug loading and release experiment indicated that this graphene nanodots inlaid porous gold electrode can be used to conveniently and efficiently control the drug release electrochemically. Not only did our work provide a benign method to electrochemically controlled drug release via electrostatic repulsion process, it also enlighten the promising practical applications of micro electrode as a drug carrier for precisely and efficiently controlled drug release via embedding in the body.

Asunto(s)

Portadores de Fármacos/química , Oro/química , Grafito/química , Nanopartículas/química , Adsorción , Línea Celular Tumoral , Preparaciones de Acción Retardada/química , Doxorrubicina/química , Doxorrubicina/metabolismo , Electroquímica , Electrodos , Humanos , Concentración de Iones de Hidrógeno , Modelos Moleculares , Conformación Molecular , Porosidad , Tetraciclina/química , Tetraciclina/metabolismo

RESUMEN

Ion beam sputtering deposition (IBSD) is used to synthesize high quality few-layer hexagonal boron nitride (h-BN) on copper foils. Compared to the conventional chemical vapor deposition, the IBSD technique avoids the use of unconventional precursors and is much easier to control, which should be very useful for the large-scale production of h-BN in the future.