N-doped Films Research Articles

(Invited) Nickel Nanoparticles Modified Carbon Film Electrodes for Detection of Sugars

Metal nanoparticles such as Pt, Au, Ni and Cu have been employed to detect various analytes including hydrogen peroxide, alcohol and sugar. Among these metal nanoparticles, Ni and Cu nanoparticles show excellent electrocatalytic activity for oxidizing sugars in alkaline solution. We employed co-sputtering and plating technique to fabricate nanostructured electrodes for enhancing electrocatalytic activity for oxidation of sugars. First example is a metal hererodimer modified carbon film electrodes. The metal nanoparticles embedded carbon film electrodes was fabricated by unbalanced magnetron (UBM) sputtering and then plated different metal nanoparticles selectively only on the embedded metal nanoparticles by utilizing overpotential difference between carbon and metal nanoparticles surfaces. Using this technique, various combinations of metals are available to fabricate vertically oriented heterodimers embedded in the carbon films. In fact, we succeeded to fabricated Ni(upper)@Pd(lower), Pt@Pd, Au@Pd, Ni@Au, Pt@Au and Pd@Au heterodimers partially embedded in the carbon film. Among these heterodimers, Ni@Pd heterodimer embedded carbon film electrode shows much higher redox reaction of Ni(OH)2 covered on the Ni nanoparticles surface compared with that on the Ni nanoparticles without Pd. The NiOOH formed by electrochemical oxidation shows much higher electrocatalytic activity for glucose compared with that formed on Ni nanoparticles modified carbon film electrode. Also, the Ni@Pd heterodimers are mechanically very stable and most of the heterodimers remained on the surface after ultrasonication treatment because surface Ni nanoparticles attached strongly to Pd nanoparticles embedded in the carbon film. In contrast, almost all Ni nanoparticles deposited on pure carbon film were detached from carbon surface after ultrasonication. The second example is a nitrogen terminated carbon film modified with Ni nanoparticles by plating. Carbon films were fabricated by UBM or RF sputtering methods and then introduced nitrogen containing functional groups. Then Ni nanoparticles were deposited by plating. The supporting effect of a N-doped carbon film induced superior crystallinity in plated Ni@Ni(OH)2 nanoparticles, which was confirmed by HAADF-STEM-EDS. This realized a much higher regeneration rate of catalytic sites (NiOOH) , leading to higher oxidation current for maltopentaose, which is well known oligosaccharide. Also, the overpotential of maltopentaose oxidation decreased significantly due to the effect of the electrostatic interaction between Ni nanoparticles and maltopentaose in the alkaline solution at pH 12.7. We also studied dependence of nitrogen concentration in the carbon film on regeneration rate of NiOOH and glucose oxidation. Both regeneration rate and electrocatalytic current of glucose oxidation increased with increasing nitrogen concentration from 0 to 3.1 %. With optimized nitrogen concentration, we could measure glucose from 25 µM to 400 µM. The enhanced activity of Ni nanoparticles could be advantageous to develop enzyme free biosensor or fuel cells using organic compounds such as sugars and oligosaccharides.[1]S. Shiba, A. Koike, S. Takahashi, D. Kato, T. Kamata and O. Niwa, ACS Nano, 16, 10589-10599 (2022).[2] S. Shiba, S. Ohta, K. Ohtani, S. Takahashi, D. Kato and O. Niwa, RSC Advances, 11, 13311-13315 (2021).

Synthesis of N-Doped Graphene Photo-Catalyst for Photo-Assisted Charging of Li-Ion Oxygen Battery.

In this work, nitrogen (N)-doped graphene film is synthesized, as a photo-catalyst, on one side of the copper foam by chemical vapor deposition and the copper foam is directly used as an electrode after porous Pd@rGO cathode loading to the other side of the foam for the photo-assisted charging of the Li-ion oxygen battery. The amount of urea (CO(NH2)2), which is used as N atom source, is optimized to get maximum photo-anodic currents from the n-type graphene films. The optical band gap and the valance band edge potential of the optimized N-doped graphene film are determined as 2.00eV and 3.71VLi+/Li, respectively. X-ray photoelectron spectra provided that the atomic percent of N atoms in the graphene film is 1.34% and the graphitic, pyrrolic and pyridinic N atom percentages are 54.01%, 42.20% and 3.79%, respectively. The photo-assisted charging tests indicated that the N-doped graphene film photo-catalyst reduced the charging potential significantly even at 1000mAg-1 (0.1mAcm-2) current density and improved the cyclic discharge-charge performance of the Li-ion oxygen battery considerably.

First-principles study of the magnetic anisotropy of ultrathin B-, C-, and N-doped FeCo films

Iron-based layered systems are of great interest because of their ability to tune effective material parameters such as magnetic anisotropy energy (MAE). The influence of the crystallographic structure of Fe, its thickness, and the presence of other layers above and below the Fe layer on magnetic parameters, such as the MAE of the studied system, is an intriguing and important topic from an application point of view. Here, we present a density functional theory (DFT) study of the magnetic anisotropy of nine-monolayer Fe, FeCo, and FeCo films with B, C, and N dopants placed in octahedral interstitial positions. The theoretical study is based on calculations using the full-potential local-orbital code FPLO and the generalized gradient approximation. The chemical disorder in the FeCo layers was modeled using the virtual crystal approximation. The structures of the layers were subjected to optimization of the geometry of the interlayer spacings and the neighborhood of the dopant sites. We determined the local magnetic moments and the excess charge at each layer position. We also identified the influence of dopant atoms on the magnetic properties of FeCo layers, such as magnetization and magnetic anisotropy.

Effect of rapid thermal annealing on the charge storage kinetics of conductive N-doped SnO2 thin film anodes for Li-ion batteries

This study focuses on the fabrication of a flexible thin film electrode composed of N-doped tin oxide (SnO2: N). The fabrication process involves sputtering SnO2 onto a Cu foil sheet using radio frequency (RF) magnetron sputtering, conducted under an N2 atmosphere. The deposited thin films are subsequently exposed to annealing treatment using rapid thermal annealing (RTA) at temperatures ranging from 200 to 400 °C. The primary objective of this study is to get an understanding of the effects of N-doping, annealing temperature on the growth of SnO2: N. as well as the influence of film thickness on the crystallographic state. We evaluate their thin-film anode performance for lithium-ion batteries (LIBs). The specific capacity of the as-deposited SnO2 thin films standing at 859 mAh g−1 when measured at 1 mA g−1. This enhanced capacity is attributed to the limited crystal growth in ultrathin SnO2, a factor that effectively combats electrode degradation while simultaneously improving the lithium-ion diffusion coefficient and electron kinetics of the electrode. However, the SnO2: N film that undergoes annealing at 400 °C demonstrates remarkable cyclic retention, reaching 82 %. This improvement is due to the enhanced electrical conductivity resulting from annealing, which prevents the aggregation of tin (Sn) and effectively accommodates the volume changes that occur in prolonged cycles. Additionally, this synchronized approach involving sputtering and RTA is proving to be a simple, efficient, and scalable method. It holds the potential to emerge as a valuable strategy to produce anode materials for lithium-ion batteries.

Low friction and wear of Nitrogen-doped diamond-like carbon films deposited on NBR with different flows of N2 by DC-MS

Utilizing a diamond-like carbon (DLC) coating on rubber surfaces is an innovative approach to improve the wear resistance and tribological characteristics of rubber. In this paper, a series of N-doped diamond-like thin films (N-DLC) were deposited on the surface of nitrile butadiene rubber (NBR) substrate by varying the flow rate of nitrogen using direct current magnetron sputtering (DC-MS) technology, and the effects of nitrogen flow rate on the surface morphology, structure, surface energy and tribological properties of N-DLC films were systematically investigated. The results show that the friction coefficients of the N-DLC films are all smaller than those of the undoped DLC films, and most importantly, the samples maintain a stable, ultra-low coefficient of friction of about 0.057 and a low wear rate of the order of 10−9 in the tribological tests at a nitrogen flow rate of 3 sccm, exhibiting excellent tribological performance. This is attributed to several key factors: higher hardness, better film-base bonding, lower surface roughness, and lower friction interface adhesion. This recognition provides insight into the preparation of N-DLC films on rubber to achieve low frictional wear.

Study on the structural, optical and electrical properties of N-doped Ga2O3 films synthesized by sol-gel method

Ga2O3 exhibits great potential for applications in solar-blind ultraviolet photo detector, high-power electronic devices and solid-state light-emitting due to its ultra-wide band gap and high Baliga figure of merit. Here, Ga2(NxO1-x)3 films with varied nitrogen contents were prepared by the sol-gel technique. XRD analysis reveals that nitrogen doping contributes for growth of greater crystalline and SEM-EDS measurements confirm that the monoclinic crystal structure of Ga2(NxO1-x)3 is maintained to doping level of 3.26wt%; FTIR information indicates that nitrogen prefers to substitute for the O1 and O2 site of Ga2O3; XPS offers evidence that nitrogen tends to occupy oxygen vacancies and generate more gallium vacancies; UV-VIS shows that impurity defects appear above valence band, and the absorption position undergoes a red shift with nitrogen above 1.32wt%; PL shows Ga2(NxO1-x)3 films can emit light of various colors under excitation at 325nm, and the acceptor level is at 1.63eV∼2eV above the valence band; The conductivity of Ga2(NxO1-x)3 films is changed from n-type to p-type when nitrogen-doping is 0.96 wt% and the I–V curve composed of Ga2(NxO1-x)3 and Ga2O3 shows PDCR = 43 under the 254nm light. Therefore, the development of nitrogen-doped β-Ga2O3 has potential opportunities for applications in photoelectric devices.

Sn-Doped Hematite Films as Photoanodes for Photoelectrochemical Alcohol Oxidation

Here, the modification of semiconductor thin film hematite photoanode by doping with Sn ions is reported. Undoped and Sn-doped hematite films are fabricated by the electrochemical deposition of FeOOH from aqueous alkaline electrolyte, followed by calcination in air. The photoanodes were tested in photoelectrocatalytic oxidation of water, methanol, ethylene glycol, and glycerol. It is shown that modification by tin dramatically increased the activity of hematite in the photoelectrochemical oxidation of alcohols upon visible light irradiation. The photoelectrocatalytic activity of Sn-modified hematite increased in the sequence of: H2O < MeOH < C2H2(OH)2 < C3H5(OH)3. The quantum yield of photocurrent in the oxidation of alcohols reached 10%. The relatively low photocurrent yield was ascribed to the recombination of photoexcited holes within the hematite layer and on surface states located at the hematite/electrolyte interface. Intensity-modulated photocurrent spectroscopy (IMPS) was used to quantify the recombination losses of holes via surface states. The IMPS results suggested that the hole acceptor in the electrolyte (alcohol) influences photocurrent both by changing the charge transfer rate in the photoelectrooxidation process and by the efficient suppression of the surface recombination of generated holes. Thin-film Sn-modified hematite photoanodes are promising instruments for the photoelectrochemical degradation of organic pollutants.

Copper sulfides (Cu7S4) nanowires with Ag anchored in N-doped carbon layers optimize interfacial charge transfer for rapid water sterilization

There are many methods of water disinfection, and how to realize low energy consumption, high efficiency and safety sterilization has always been a research hotspot. In this work, Cu7S4 nanowires were grown on copper foam, and coated with N-doped carbon layer and Ag particles, which not only improved the conductivity and local field enhancement regions of the material, but also improved the durability and mechanical stability of Cu7S4. DFT (Density functional theory) calculation shows that different kinds of N doping make the electron difference density and work function of the surrounding C different, which leads to high carrier transport capacity at the interface, and Ag anchored in N-doped carbon films can adsorb O2. The band gap of the material is 2.12 eV, and the material has the potential to generate superoxide anion under energy excitation. Under the condition of 6 V voltage and 1000 mL min−1 water flow rate, the long-term water filtration sterilization of high-concentration bacteria can be realized, and the removal efficiency can still reach 99% after 8 h continuous treatment. This work has great application prospects for the purification of highly polluted water in the future.

Research on Equipment of Magnetron Sputtering and Deposition of ZnO Films

The parts of magnetron sputtering system were given in the paper. Meanwhile, we analyzed the working theory of magnetron sputtering. After pure zinc oxide (ZnO) film was grown, N-doped films was Prepared in NH3-O2-Ar atmosphere using zinc as a target, and Al-doped and N+Al codoped ZnO films were grown by co-sputtering technique using zinc and aluminum as targets. AFM showed the crystal quality of the Films. The results of experiment demonstrate that high-quality films have been achieved by this technique, and research on ZnO films can be done by the equipment.

Nitrogen-Doped Single-Walled Carbon Nanotubes by Floating-Catalyst CVD Process

Due to the properties of single-walled carbon nanotube (SWCNT), thin film SWCNTs have been used for many versatile applications. Direct synthesis of the nanotube films with desired electronic structures without prerequisite of post treatment process then becomes one important step. Here, we present the synthesis of nitrogen-doped SWCNTs by floating-catalyst chemical vapor deposition process. With low nitrogen level incorporated into the sp2 carbon network, substitutional and pyridinic nitrogens become predominance. The electronic structure of N-doped SWCNT film could be changed into n-type doping. The localized structures of carbon and nitrogen bonding environments were also revealed by x-ray absorption spectroscopy. The formation of p-n junction was also obtained from the I-V characteristic of N-doped SWCNT heterojunction diode revealing n-type behavior of the sample.

Efficiency of cathodic arc-grown N-doped TiO2 films for the photocatalytic reduction of Cr(VI) under UV-Vis irradiation

The photocatalytic activity of undoped and N-doped TiO2 anatase films with different thicknesses prepared by cathodic arc deposition on glass substrates is reported. After TiO2 deposition, the doping of the films was carried out by plasma immersion ion implantation in a nitrogen environment. The composition of the films was studied by x-ray photoelectron spectroscopy, the surface morphology was analyzed by atomic force microscopy and the crystalline structure was examined by x-ray diffraction. The thickness was determined by observing the film cross section with scanning electron microscopy. The transmittance of the films in the UV-Vis range was studied as well. The photocatalytic activity of the films was evaluated through the efficiency in the reduction of Cr(VI) in the presence of ethylenediaminetetraacetic acid under UV-Vis irradiation. N-doped films presented a higher photocatalytic efficiency than undoped films: Cr(VI) reduction after 5 h irradiation augmented from 58% (pure TiO2) to 85% (N-doped TiO2) for films of 300 nm thickness, and from 69% to 85% for films with a thickness of 440 nm. On the other hand, pure TiO2 films of 790 nm thickness were more efficient (99% of Cr(VI) reduction) but the effect of doping on the photocatalytic activity was negligible.

Long-Lived Photo-Response of Multi-Layer N-Doped Graphene-Based Films.

New insights into the mechanism of the improved photo(electro)catalytic activity of graphene by heteroatom doping were explored by transient transmittance and reflectance spectroscopy of multi-layer N-doped graphene-based samples on a quartz substrate prepared by chitosan pyrolysis in the temperature range 900-1200 °C compared to an undoped graphene control. All samples had an expected photo-response: fast relaxation (within 1 ps) due to decreased plasmon damping and increased conductivity. However, the N-doped graphenes had an additional transient absorption signal of roughly 10 times lower intensity, with 10-50 ps formation time and the lifetime extending into the nanosecond domain. These photo-induced responses were recalculated as (complex) dielectric function changes and decomposed into Drude-Lorentz parameters to derive the origin of the opto(electronic) responses. Consequently, the long-lived responses were revealed to have different dielectric function spectra from those of the short-lived responses, which was ultimately attributed to electron trapping at doping centers. These trapped electrons are presumed to be responsible for the improved catalytic activity of multi-layer N-doped graphene-based films compared to that of multi-layer undoped graphene-based films.

Photocatalytic Activity of N-Doped ZrO2 Thin Films Determined by Direct and Indirect Irradiation.

In this paper, we investigate the decomposition of a toxic organic compound, Rhodamine B, by the photocatalytic activities of undoped and nitrogen-doped ZrO2 thin films, deposited using the HiPIMS technique. The investigation was performed in the presence and in the absence of H2O2, for two types of experimental arrangements: the irradiation of the films, followed by dipping them in the Rhodamine B solutions, and the irradiation of the films dipped in the solution. The two situations were named "direct irradiation" and "indirect irradiation", respectively. Methods like XRD, AFM, XPS, DRS, water/film surface contact angle, and spectrophotometry were used to obtain information on the films' structure, surface morphology, elemental composition of the films surface, optical band gap, hydrophilicity, and photocatalytic activity, respectively. All these properties were described and correlated. By N-doping ZrO2, the films become absorbent in the visible domain, so that the solar light could be efficiently used; the films' hydrophilic properties improve, which is an important fact in self-cleaning applications; and the films' photocatalytic activity for the decomposition of Rhodamine B becomes better. The addition of hydrogen peroxide acted as an inhibitor for all systems and not as an accelerator of the photocatalytic reactions as expected.

Enhancing thermochromic properties of VO2 amorphous films on glass substrates by Sn-W co-doping

Co-doping is an effective method for VO2 films to meet the requirements of smart window applications. In this research, we prepared pure VO2, Sn-doped, and Sn-W co-doped amorphous films on glass substrates. Compared with pure and Sn-doped VO2 films, Sn-W co-doped samples showed better thermochromic properties. For the 4.8 % Sn-2.1 % W co-doped sample, the luminous transmittance (Tlum) reached 76 %, the metal-insulator transition (MIT) temperature (Tc) decreased to 46.7 °C, the solar transmittance modulation capacity (ΔTsol) was maintained at around 5.2 %, and the near-infrared modulation capacity (ΔTIR) was up to 13.5 %. These results show that co-doping Sn and W into VO2 is feasible for smart window applications.

Deposition of TiOx and N-TiOx by dielectric barrier discharge at atmospheric pressure

Over the past years, atmospheric pressure deposition assisted by plasma has attracted interest due to its low cost. Among other materials deposited by this technology, titanium dioxide (TiO2) is very popular, mostly due to its good photocatalytic properties. However, due to intrinsic drawbacks of the process, the control of the deposition parameters needs to be fine-tuned to obtain a thin film presenting the expected properties. Here we report the deposition of TiOx and N-doped TiOx thin films by dielectric barrier discharge at atmospheric pressure (AP-DBD) plasma with titanium (IV) isopropoxide and oxygen as reactants, and argon as a working gas during 10 min. In the first part, we highlight the advantages of heating the substrate at 400 °C during the deposition. Then, the influence of the oxygen content and power on the morphology and composition is reported. In the second part, we demonstrate the successful doping of the structure with nitrogen by adding ammonia (NH3) to the working gas. Through a screening over deposition parameters (i.e. oxygen content and power), the lowest bandgap reachable was 3.22 eV for a working gas composed of 1.8 vol% of NH3, 5, and 10 vol% of O2, and a power of 75 W during the film deposition. Evaluating the formation of oxygen vacancies in the TiOx films and the N doping, we were able to tentatively explain the observed evolution of the bandgap.

Mo Single-Atom Nanozyme Anchored to the 2D N-Doped Carbon Film: Catalytic Mechanism, Visual Monitoring of Choline, and Evaluation of Intracellular ROS Generation.

Single-atom nanozymes (SANs) have attracted great attention in constructing devices for instant biosensing due to their excellent stability and atom utilization. Here, Mo atoms were immobilized in 2D nitrogen-doped carbon films by cascade-anchored one-pot pyrolysis to obtain Mo single-atom nanozyme (Mo-SAN) with high atomic loading (4.79 wt %) and peroxidase-like activity. The coordination environment and enzyme-like activity mechanism of Mo-SAN were studied by combining synchrotron radiation and density functional theory. The strong oxophilicity of single-atom Mo makes the catalytic center more capable of transferring electrons to free radicals to selectively generate •OH in the presence of H2O2. Choline oxidase and Mo-SAN were used as signal opening unit and signal amplification unit, respectively. Combining the portability and visualization functions of smartphone and test strips, a paper-based visual sensing platform was constructed, which can accurately identify choline at a concentration of 0.5-35 μM with a limit of detection as low as 0.12 μM. The recovery of human serum samples was 96.4-102.2%, with an error of less than 5%. Furthermore, the potential of Mo-SAN to efficiently generate toxic •OH in tumor cells was intuitively confirmed. This work provides a technical and theoretical basis for designing highly active SANs and detecting neurological markers.

Multilevel optoelectronic hybrid memory based on N-doped Ge2Sb2Te5 film with low resistance drift and ultrafast speed

Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed, scalable and non-volatile characteristics. However, the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory. Here, N-doped Ge2Sb2Te5-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed. The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout. Results show that when N content is 27.4 at.%, N-doped Ge2Sb2Te5 film possesses high ten-year data retention temperature of 175 °C and low resistance drift coefficient of 0.00024 at 85 °C, 0.00170 at 120 °C, and 0.00249 at 150 °C, respectively, owing to the formation of Ge–N, Sb–N, and Te–N bonds. The SET/RESET operation speeds of the film reach 520 ps/13 ps. In parallel, the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude. Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients. Therefore, the N-doped Ge2Sb2Te5 thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.

Optoelectronic properties of undoped and N-doped ZnTe films grown by RF sputtering: Effect of the substrate temperature and N nominal concentration

Undoped and N-doped ZnTe films were deposited by RF magnetron sputtering. Undoped ZnTe films were grown varying the substrate temperature, while N-doped ZnTe films were obtained at 360 °C with different N nominal concentrations. The XRD and HR-TEM results showed that ZnTe and Te phases coexist in undoped and N-doped ZnTe films. Raman analysis showed the presence of signals associated with tellurium-rich phases as well as the mode of Zn-Te bond. The incorporation of N in the ZnTe films was corroborated through XPS measurements. The optical characterization showed that the increase in N nominal concentration in the ZnTe lattice reduces the bandgap from 2.38 eV (undoped) to 1.48 eV for the highest nominal N content. The electrical characterization showed that doping with nitrogen reduces the resistivity in four orders of magnitude. CdS/CdTe solar cells were fabricated using undoped and N-doped films to evaluate their performance through the J-V curves.

Impact of metal doping on the physical characteristics of anatase titanium dioxide (TiO2) films

This study focuses on the synthesis of anatase titanium dioxide (TiO2) films doped with metals (Mg, Ni, and Sn) using the sol–gel dip coating technique. The main objective was to investigate the chemical, crystal, and morphological structure of the Mg-, Ni-, and Sn-doped TiO2 films. The doping mechanism between the metals and the TiO2 films was confirmed through Fourier-transform infrared (FTIR) spectroscopy, which revealed characteristic absorption bands associated with the doping process. Additionally, X-ray diffraction (XRD) patterns confirmed that all films maintained an anatase phase, indicating the preservation of the desired crystal structure. Furthermore, the introduction of Mg and Sn metals into the TiO2 film resulted in a decrease in the crystallite size, reducing it from 53 to 16 nm and 24 nm, respectively. Conversely, the incorporation of Ni into the TiO2 film increased the crystallite size to 72 nm. Moreover, the presence of these metals in the TiO2 film contributed to a smoother film surface, thereby enhancing the hydrophilicity of the films. The optical bandgap of the TiO2 films decreased with the introduction of Mg, Ni, and Sn, exhibiting values of 3.24 eV, 3.11 eV, and 3.15 eV, respectively, compared to the original value of 3.33 eV. Additionally, the electrical conductivity (σ-value) increased upon the introduction of Mg, Ni, and Sn, reaching values of 0.25 mS.cm−1, 0.37 mS.cm−1, and 2.5 mS.cm−1, respectively. Overall, this work provides insights into the chemical, crystal, and morphological characteristics of Mg-, Ni-, and Sn-doped TiO2 films.

Infrared and Terahertz Spectra of Sn-Doped Vanadium Dioxide Films

This work reports the effect of tin (Sn) doping on the infrared (IR) and terahertz (THz) properties of vanadium dioxide (VO2) films. The films were grown by hydrothermal synthesis with a post-annealing process and then fully characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and temperature-controlled electrical resistivity as well as IR and THz spectroscopy techniques. Utilizing (NH4)2SnF6 as a Sn precursor allows the preparation of homogeneous Sn-doped VO2 films. Doping of VO2 films with Sn led to an increase in the thermal hysteresis width while conserving the high modulation depth in the mid-IR regime, which would be beneficial for the applications of VO2 films in IR memory devices. A further analysis shows that Sn doping of VO2 films significantly affects the temperature-dependent THz optical properties, in particular leading to the suppression of the temperature-driven THz transmission modulation. These results indicate Sn-doped VO2 films as a promising material for the development of switchable IR/THz dichroic components.