Sn-doped Indium Oxide Research Articles

Plasma-enhanced atomic layer deposition of Sn-doped indium oxide semiconductor nano-films for thin-film transistors

Sn-doped indium oxide (ITO) semiconductor nano-films are fabricated by plasma-enhanced atomic layer deposition using trimethylindium (TMIn), tetrakis(dimethylamino)tin (TDMASn), and O2plasma as the sources of In, Sn and O, respectively. A shared temperature window of 150 °C- 200 °C is observed for the deposition of ITO nano-films. The introduction of Sn into indium oxide is found to increase the concentration of oxygen into the ITO films and inhibit crystallization. Furthermore, two oxidation states are observed for In and Sn, respectively. With the increment of interfaces of In-O/Sn-O in the ITO films, the relative percentage of In3+ions increases and that of Sn4+decreases, which is generated by interfacial competing reactions. By optimizing the channel component, the In0.77Sn0.23O1.11thin-film transistors (TFTs) demonstrate high performance, includingμFEof 52.7 cm2V-1s-1, and a highION/IOFFof ∼5 × 109. Moreover, the devices show excellent positive bias temperature stress stability at 3 MV cm-1and 85 °C, i.e. a minimalVthshift of 0.017 V after 4 ks stress. This work highlights the successful application of ITO semiconductor nano-films by ALD for TFTs.

Multilayer and Thin Transparent Conducting Oxide Fabrication Using RF Magnetron Sputtering on Flexible Substrates

In this work, the fabrication of multilayered transparent conductive oxides (TCOs), ZnO–Ag–ZnO (Z-TCO) and AZO–Ag–AZO (AZ-TCO), on flexible polyethylene terephthalate (PET) substrate using radio frequency (RF) magnetron sputtering is reported, with the optical and electrical properties comparable to those of the commercially available Sn-doped indium oxide (ITO) on the PET substrate. The growth of Z-TCO and AZ-TCO layers on PET (with surface roughness ~5 – 7 nm) shows similar surface characteristics to that on the glass substrate. The multilayered Z-TCO and AZ-TCO (total thickness ~70 nm) with 10 nm of Ag thickness (named Z-2 and AZ-2, respectively) exhibit a maximum transparency of 82.7% and 86.4%, at 515 and 498 nm, respectively. The AZ-2 layer has a lower electrical resistivity of 3.92 × 10−5 Ω cm with a lower sheet resistance of 5.6 Ω/sq, whereas for ITO on PET these values are 2.62 × 10−4 Ω cm and 14.5 Ω/sq, respectively. The AZ-2 layer also gives an excellent figure of merit (FoM) of 21.3 × 10−3 Ω−1, which is better than the FoM for ITO PET (17.3 × 10−3 Ω−1). Therefore, the flexible multilayer TCOs prepared using RF magnetron sputtering on PET substrates on a large area can have better optoelectronic properties than commercial flexible ITO coating and can be used in flexible optoelectronic devices.

Facile fabrication of NiO foam@Sn-doped In2O3 nanowire heterosturctures for highly sensitive ethylene glycol gas sensors at low temperatures

Ethylene glycol is odorless and harmful to human beings. However, the high operating temperature and the low gas response of the ethylene glycol sensors limit their wide applications. Herein, p-type nickel oxide foam/ n-type tin-doped indium oxide nanowires composite (NTO) has been fabricated for ethylene glycol gas sensing. The NTO composite was prepared by complete oxidation of Ni foam at high temperature, then Sn-doped indium oxide (ITO) nanowires were grown on NiO foam by chemical vapor deposition. The assembled NTO sensor exhibits a unique response (Rg/Ra=160.72) to 100 ppm ethylene glycol at a low temperature of 125 ℃, and a fast response/ recovery time (8.7 s/ 19.3 s). This excellent gas-sensitive performance of NTO sensors can be attributed to the formation of p/n heterojunctions and the In and Sn doping of NiO during ITO growth. This fabrication method provides an effective strategy for building NiO-based heterostructures for high-performance gas sensors.

Fabrication and Characterization of Plasmonic Au Nanoparticles on ITO-Coated Glass Sheets

We report here the fabrication of sputter-deposited Au nanoparticles on ITO (Sn-doped indium oxide)-coated glass substrate. The effect of varying annealing parameters, viz., time and temperature in conjunction with varying thickness parameters has been thoroughly investigated. Synthesized Au nanoparticles were characterized using a field emission scanning electron microscope (FE-SEM), Rutherford backscattering (RBS) measurement, X-ray diffraction (XRD), and optical absorbance spectroscopy. The role of annealing temperature and time duration on the evolution of Au nanoparticles has been discussed in detail based on optical absorbance spectroscopy. The present study shows that 5 nm thickness Au thin film which was annealed at 500 °C for 90 min exhibited the strongest surface plasmon resonance (SPR) effect.

Origin of operating voltage increase in deep UV light-emitting diodes with ITO/Al reflector

In an attempt to further elucidate the operating voltage increase in a vertical UV-C LED with p-electrode composed of transparent conducting Sn-doped indium oxide (ITO)/Al reflector, the interface formation between ITO and Al thin film was studied by using scanning transmission electron microscopy in combination with electron energy loss spectroscopy. It was confirmed that the oxidized layer was formed at the interface of the ITO/Al electrode in accordance with the thermal annealing. It was found that not only the thickness of oxide formation grew with the increased annealing temperature, the content of oxygen also increased. Moreover, it was also ascertained that the prolonged annealing time at high temperature induced the indium diffusion into the Al-oxide layer.

Fabrication and characterization of p-Si/n-In2O3 and p-Si/n-ITO junction diodes for optoelectronic device applications

Octahedral novel indium tin oxide (ITO) films were fabricated on glass substrates. The dopant material tin (Sn) was added at different concentration like 0, 5, 10, 15 weight percentage (wt.%) with indium oxide precursor and the synthesis was done by spray pyrolysis technique. XRD studies revealed proper doping of tin in indium oxide crystal lattice structure. The surface morphology of ITO films confirmed the octahedral structure of crystallites formed and the variation in size of the microstructures with doping concentration. The bonding states of indium and tin with oxygen and composition of ITO films were inspected through XPS. The average roughness of films varied from 26.65 to 139.08 nm. The optical properties studied from UV-VIS studies showed a sharp increase in bandgap from undoped to 5 wt.% Sn doped indium oxide films followed by slight decrease in values with the increase in doping concentration. The photoluminescence excitation of ITO films showed a rapid fall in the peak intensity values due to the quenching of oxygen vacancies and a slight blue shift in emission confirms the doping of tin indium oxide. The resistivity values tremendously decrease with increase in doping concentration, that is tin doping improves conduction which was observed using two probe method. The fabricated p-Si/n-ITO junction diode shows that the ITO is degenerated semiconductor and the photo response is exhibited with a high ideality factor of 8.98 in dark and 6.46 in visible light exposed conditions respectively.

High mobility Ti, Zr and Ga-codoping In2O3 transparent conductive oxide films prepared at low temperatures

High mobility transparent conductive Zr, Ti and Ga-doped indium oxide (ITGZO) films were deposited by radio frequency (RF) magnetron sputtering method at the low deposition temperature. The effects of deposition temperatures on structural, electrical, and optical properties of ITGZO films were investigated in this work. High mobility of 94 cm2/V S was achieved at the deposition temperature of 70 °C along with the annealing process. Furthermore, the optical transmittance of ITGZO films has increased by 18% at the infrared wavelength region from 1500 to 2580 nm; compared to the typical Sn-doped indium oxide (ITO) films, this excellent transmittance is mainly attributed to the less free carrier absorption (FCA) thanks to the low carrier concentration of less than 2.0 × 1020 cm−3. In addition, the surface morphology of ITGZO films demonstrated that Ga element would precipitate on the film surface when oxygen was insufficient during the film growth, which indicates that Ga element exists as an oxidation state rather than interstitial atom in ITGZO films; correspondingly, the impurity ion scattering of carriers would be effectively suppressed, which accounts for the high mobility of ITGZO films. Moreover, ITGZO film shows a very low extinction coefficient (k) of 10–4 at 633 nm after annealing, which implies almost zero absorption loss from ITGZO films. Based on the higher mobility and better optical properties, it is expected that ITGZO film is a promising alternative material substituting for the typical ITO film in the advanced optoelectronic devices.

New approach to SnO2-based transparent conducting oxides incorporating synergistic effects of Au nano particles and microwave irradiation

Recently, transparent conducting oxides (TCOs) have attracted increasing attention in the development of electronic devices and energy harvesting applications. Standard materials used as TCOs are Sn-doped indium oxide (ITO) and F-doped tin oxide (FTO), which are ternary systems and require a doping process. Here, we introduce the synergistic effect of using microwave (MW) irradiation and Au nanoparticles (NPs) together on tin dioxide (SnO2) thin films grown by atomic layer deposition (ALD), which have a binary system and do not need any additional doping process. For comparison to as-deposited SnO2 thin films, we prepared MW-irradiated SnO2 thin films with and without Au NP decoration. SnO2 thin films with Au NPs added during MW irradiation have carrier concentration, Hall mobility, and resistivity of 1.45 × 1022 cm−3, 5.4 cm2/Vs, and 7.93 × 10−5 Ω cm, respectively. Compared with as-deposited SnO2 thin films, these electrical properties are significantly enhanced, and plasmonic effects also occurred due to the presence of Au NPs. The enhanced properties are mainly attributed to generation of oxygen vacancies in SnO2 thin films. Our results demonstrate the potential of using SnO2 thin films as binary system TCOs, and point to the synergistic effects of using MW and Au NPs together.

Optimized SrVOx/Ag/SrVOx Multilayers As High Transparency Electrodes for UV Optoelectronic Devices

GaN-based ultraviolet LEDs are important for their use in various applications such as space-to-space communications, curing, sterilization, etc. For these applications, the development of high-efficiency UV LEDs is needed. However, UV LEDs show relatively lower external quantum efficiencies than visible LEDs. To enhance the performance of UV optoelectronic devices by increasing light extraction, it is essential to develop p-type transparent conducting electrodes (TCEs) with high transparency in the UV region. Sn-doped indium oxide (ITO) is typical material for transparent conducting electrodes (TCEs) because of its low resistivity (< 10-4 Ω·cm) and high transmittance (> 85%) in the visible range. However, ITO has large light absorption below 400 nm wavelength and the poor electrical properties when it is thinner than 50 nm. Thus, there is a need for alternative TCEs that have high transmittance in the UV light region (200 – 400 nm). Extensive studies have been conducted to develop TCEs such as graphene, CNT, metal nanowire, and oxide/metal/oxide (OMO) multilayer. Among them, the OMO structure can be a good candidate for TCEs, because the mid-metal layer acts as a conduction path and the oxide layers can lead to zero reflection conditions.In this study, we used SrVOx (SVO) films to develop UV-transparent multilayer and investigated their structural, optical, and electrical properties as functions of SVO and Ag thickness by means of UV-VIS spectrometer, Hall-measurement, and transmission electron microscopy. Unlike ITO film, SVO film exhibited high transmittance (> 80%) up to 320 nm. It was shown that the SVO film showed larger optical bandgap (4.3 eV) than that of ITO (3.7 eV). For the OMO structures with Ag thickness of 15 nm, the sheet resistance was in the range 2.76 – 3.15 Ω/sq, depending on the SVO thickness. In particular, SVO (25 nm)/Ag (15 nm)/SVO (25 nm) sample exhibited the highest Haacke’s figure of merit (FOM) of 144.5 x 10-3 Ω-1 where the average transmittance of the OMO was 91.5% over the 360 – 400 nm wavelength. For the 25 nm-thick SVO-based OMO films, the transmittance and sheet resistance gradually decreased with increasing Ag thickness from 9 nm to 21 nm. For example, the sheet resistance of SVO/Ag/SVO samples was in the range 1.97 – 6.48 Ω/sq and the transmittance varied from 82.6 to 95.5%. Among these samples, SVO/Ag (15 nm)/SVO sample showed the highest FOM value. Rigorous coupled-wave analysis (RCWA) simulations were performed to understand the measured transmittance behavior and zero reflection condition in the SVO/Ag/SVO structure. These results imply that SVO-based OMO structure could be a potentially important TCEs for the fabrication of high-efficiency UV optoelectronic devices. Figure 1

The enhanced Coulomb interaction in three-dimensional indium tin oxide films

The Coulomb interaction effect in disordered conductors has long been a topic of fundamental importance and intense attention. Here, we systematically study the influence of this effect on the electrical transport of a series of ∼1 μm thick Sn-doped indium oxide (ITO) films grown at different oxygen partial pressures. We find that both the electrical conductivity σ and Hall coefficient RH vary linearly with T from ∼35 K down to ∼4 K. The extracted electron screening factor F~σ of each film is nearly in agreement with the corresponding theoretical value. Moreover, the F~σ values increase with decreasing carrier concentration in the ITO films, which originates from less screening effect of electrons and enhanced Coulomb interaction. These features are consistent with conventional three-dimensional Coulomb interaction theories. We explore the long-standing puzzle of the carrier concentration dependence of F~σ. Our results provide the fundamental physics to modulate the intensity of the Coulomb interaction effect, which may be useful to optimize the performance of electron transport for nanoscale electronic devices.

Dual-Mode Infrared Absorption by Segregating Dopants within Plasmonic Semiconductor Nanocrystals

When aliovalent dopants are sufficiently segregated to the core or near the surface of semiconductor nanocrystals, charge carriers donated by the dopants are also segregated to the core or near the surface, respectively. In Sn-doped indium oxide nanocrystals, we find that this contrast in free charge carrier concentration creates a core and shell with differing dielectric properties and results in two distinctly observable plasmonic extinction peaks. The trends in this dual-mode optical response with shell growth differ from core/shell nanoparticles composed of traditional plasmonic metals such as Au and Ag. We developed a model employing a core/shell effective medium approximation that can fit the dual-mode spectra and explain the trends in the extinction response. Lastly, we show that dopant segregation can improve sensitivity of plasmon spectra to changes in refractive index of the surrounding environment.

Optimized SrVO3/Ag/SrVO3 Multilayers As High Transparency Electrodes for UV Optoelectronic Devices

GaN-based ultraviolet(UV) LEDs are important for their use in various applications such as space-to-space communications, curing, sterilization, etc. For these applications, the development of high-efficiency UV LEDs is needed. However, UV LEDs show relatively lower external quantum efficiencies than visible LEDs. To enhance the performance of UV optoelectronic devices by increasing light extraction, it is essential to develop p-type transparent conducting electrodes (TCEs) with high transparency in the UV region. Sn-doped indium oxide (ITO) is typical material for transparent conducting electrodes (TCEs) because of its low resistivity (< 10-4 Ω·cm) and high transmittance (> 85%) in the visible range. However, ITO has large light absorption below 400 nm wavelength and the poor electrical properties when it is thinner than 50 nm. Thus, there is a need for alternative TCEs that have high transmittance in the UV light region (200 – 400 nm). Extensive studies have been conducted to develop TCEs such as graphene, CNT, metal nanowire, and oxide/metal/oxide (OMO) multilayer. Among them, the OMO structure can be a good candidate for TCEs, because the mid-metal layer acts as a conduction path and the oxide layers can lead to zero reflection conditions.In this study, we used SrVO3 films to develop UV-transparent multilayer and investigated their structural, optical, and electrical properties as functions of SrVO3 and Ag thickness by means of UV-VIS spectrometer, Hall-measurement, and transmission electron microscopy. Unlike ITO film, SrVO3 films exhibited high transmittance (> 80%) up to 320 nm. It was shown that the SrVO3 film showed larger optical bandgap (4.3 eV) than that of ITO (3.7 eV). For the OMO structures with Ag thickness of 15 nm, the sheet resistance was in the range 2.76 – 3.15 Ω/sq, depending on the SrVO3 thickness. In particular, SrVO3 (25 nm)/Ag (15 nm)/SrVO3 (25 nm) sample exhibited the highest Haacke’s figure of merit (FOM) of 144.5 x 10-3 Ω-1 where the average transmittance of the OMO was 91.5% over the 360 – 400 nm wavelength. For the 25 nm-thick SrVO3-based OMO films, the transmittance and sheet resistance gradually decreased with increasing Ag thickness from 9 nm to 21 nm. For example, the sheet resistance of SrVO3/Ag/SrVO3 samples was in the range 1.97 – 6.48 Ω/sq and the transmittance varied from 82.6 to 95.5%. Among these samples, SrVO3/Ag (15 nm)/SVO sample showed the highest FOM value. Rigorous coupled-wave analysis (RCWA) simulations were performed to understand the measured transmittance behavior and zero reflection condition in the SrVO3/Ag/SrVO3 structure. These results imply that SrVO3-based OMO structure could be a potentially important TCEs for the fabrication of high-efficiency UV optoelectronic devices.

Calcium incorporated copper indium oxide thin films - a promising candidate for transparent electronic applications

This paper reports the possibility to fabricate transparent diodes with the configuration: Fluorine doped Tin Oxide/n-type copper indium oxide/p-type calcium doped copper indium oxide/Silver with better rectification ratio than that of the diodes with Sn-doped Copper Indium Oxide as the n-counterpart of p- calcium doped copper indium oxide. The ideality factor and turn on voltage of the former diodes are determined as ~1.1 and ~ 0.68 respectively while for the latter types they are ~2.38 and ~ 0.5 V respectively. In addition to this, the paper details the structural, morphological, optoelectronic and electrical properties of delafossite crystalline p-type calcium doped copper indium oxide thin films deposited by activated reactive evaporation in oxygen plasma followed by post air annealing. The temperature of crystallization of the films obtained here is the lowest crystallization temperature reported for the delafossite formation of this compound till date. Electrical transport mechanisms governing conductivities in the temperature range 55 – 430 K are also investigated.

Characterization of Zn coated Radio Frequency sputtered AZO thin films

Transparent conducting oxides (TCOs) have become an essential part of today’s life through their application in touch screen technology. The growing interest for superior and cheap transparent conducting films, primarily driven by the smart televisions and phones market, has led to renewed efforts to develop novel TCOs. Currently, the most widely used material for transparent conducting applications is Sn-doped indium oxide (ITO), but this material is expensive. Al-Doped zinc oxide (AZO) is among the few metal oxides which can replace costly tin doped indium oxide (ITO) due to many properties similar to it. Thin films of AZO of different thickness 100 nm, 200 nm, 300 nm were deposited on glass substrates using Al doped ZnO target by RF magnetron sputtering system and 15 nm Zn layer on top of it by DC magnetron sputtering system and annealed in inert environment. These films show a carrier concentration of 2.28× 1021 cm-3, mobility of 27 cm2/V-s and resistivity of 10-4 Ω-cm. Such a low value of resistivity is attributed to a dense compact columnar morphology of the sputtered films as evident from FESEM micrograph. The nanocolumns of such close proximity with higher surface related defects increase the carrier concentration enormously. As a result, compact columnar structure improves conduction process and increases electrical conductivity which is comparable to the standard TCO characteristics used in the optoelectronic devices.

Evaluation of Sn-Doped Indium Oxide Film and Interface Properties on a-Si Formed by Reactive Plasma Deposition

In pursuit for the improvement of heterojunction Si solar cell performance, we evaluated Sn-doped Indium oxide (ITO)/a-Si structure by using conventional and hard X-ray photoelectron spectroscopy (XPS, HAXPES) to identify the cause of solar cell performance degradation. HAXPES allows us to evaluate the SiOx layer at the ITO/a-Si interface non-destructively. The SiOx formation at the ITO/a-Si interface leads to an increase the contact resistance, which can be reduced by post deposition annealing (PDA). In addition, PDA promoted the evaluation of Fermi level, the precipitation of ITO component in a-Si layer, and the increase of interface roughness. Before PDA, the diffusion of Sn atoms in a-Si was observed. Furthermore, it was also confirmed by PDA that Si atoms were diffused to ITO. These reaction at the ITO/a-Si interface may be part of the degradation factor of the Si solar cells.

Highly Conductive and Broadband Transparent Zr-Doped In2O3 as Front Electrode for Solar Cells

Broadband transparent and highly conducting electrodes are key to avoid parasitic absorption and electrical losses in solar cells. Here, we propose zirconium-doped indium oxide (IO:Zr) as a transparent electrode intrinsically meeting both requirements and demonstrate its application as the front electrode in silicon heterojunction (SHJ) solar cells. The exceptional properties of this material rely on the combination of high-doping and high electron mobilities, achieving with this a wide optical band gap (3.5–4 eV), low free carrier absorption, and high lateral conductivity. A single film of IO:Zr has an electron mobility of 100 cm2/Vcs with a carrier density of 2.5–3 × 1020 cm–3, resulting in a sheet resistance of around 25 Ω/sq for 100-nm-thick films. Their implementation as a front electrode in SHJ solar cells results in an important gain in current density as compared to the standardly used Sn-doped indium oxide. This is due to reduced parasitic absorption in both, the UV and IR, as confirmed by external quantum efficiency measurements. SHJ devices with the optimized IO:Zr front electrode, resulting in current densities of 40 mA/cm2, a fill factor of 80%, and a conversion efficiency of 23.4%.

Impacts of surface depletion on the plasmonic properties of doped semiconductor nanocrystals.

Degenerately doped semiconductor nanocrystals (NCs) exhibit a localized surface plasmon resonance (LSPR) in the infrared range of the electromagnetic spectrum. Unlike metals, semiconductor NCs offer tunable LSPR characteristics enabled by doping, or via electrochemical or photochemical charging. Tuning plasmonic properties through carrier density modulation suggests potential applications in smart optoelectronics, catalysis and sensing. Here, we elucidate fundamental aspects of LSPR modulation through dynamic carrier density tuning in Sn-doped In2O3 (Sn:In2O3) NCs. Monodisperse Sn:In2O3 NCs with various doping levels and sizes were synthesized and assembled in uniform films. NC films were then charged in an in situ electrochemical cell and the LSPR modulation spectra were monitored. Based on spectral shifts and intensity modulation of the LSPR, combined with optical modelling, it was found that often-neglected semiconductor properties, specifically band structure modification due to doping and surface states, strongly affect LSPR modulation. Fermi level pinning by surface defect states creates a surface depletion layer that alters the LSPR properties; it determines the extent of LSPR frequency modulation, diminishes the expected near-field enhancement, and strongly reduces sensitivity of the LSPR to the surroundings.

An Optically Flat Conductive Outcoupler Using Core/Shell Ag/ZnO Nanochurros

Transparent conductive electrodes (TCEs) featuring a smooth surface are indispensable for preserving pristine electrical characteristics in optoelectronic and transparent electronic devices. For high-efficiency organic light emitting diodes (OLEDs), a high outcoupling efficiency, which is crucial, is only achieved by incorporating a wavelength-scale undulating surface into a TCE layer, but this inevitably degrades device performance. Here, an optically flat, high-conductivity TCE composed of core/shell Ag/ZnO nanochurros (NCs) is reported embedded within a resin film on a polyethylene terephthalate substrate, simultaneously serving as an efficient outcoupler and a flexible substrate. The ZnO NCs are epitaxially grown on the {100} planes of a pentagonal Ag core and the length of ZnO shells is precisely controlled by the exposure time of Xe lamp. Unlike Ag nanowires films, the Ag/ZnO NCs films markedly boost the optical tunneling of light. Green-emitting OLEDs (2.78 × 3.5 mm2 ) fabricated with the Ag/ZnO TCE exhibit an 86% higher power efficiency at 1000 cd m-2 than ones with an Sn-doped indium oxide TCE. A full-vectorial electromagnetic simulation suggests the suppression of plasmonic absorption losses within their Ag cores. These results provide a feasibility of multifunctional TCEs with synthetically controlled core/shell nanomaterials toward the development of high-efficiency LED and solar cell devices.

Localized Surface Plasmon Coupling between Mid-IR-Resonant ITO Nanocrystals.

Sn-doped indium oxide (ITO) nanocrystals (NC) provide tunable localized surface plasmon resonance in the mid-infrared. To evaluate the applicability of these n-doped plasmonic semiconductors in field-enhanced spectroscopies, it is necessary to assess how the low, free-electron density affects the E-field localization and plasmon coupling in NC films when compared to metal nanoparticles (NP). In this article, we investigate plasmon coupling between approximate 6 nm diameter ITO NC on the collective resonance and quantify the effect of the electromagnetic field enhancement on the absorbance signal of surface-attached ligands in NC films and monolayers with different ratios of doped and undoped indium oxide NC.

Hierarchical Ag nanostructures on Sn-doped indium oxide nano-branches: super-hydrophobic surface for surface-enhanced Raman scattering.

Herein, we fabricated a super-hydrophobic SERS substrate using Sn-doped indium oxide (Indium-tin-oxide: ITO) nano-branches as a template. ITO nano-branches with tens of nanometer diameter are first fabricated through the vapor–liquid–solid (VLS) growth to provide roughness of the substrate. 10 nm thickness of Ag thin film was deposited and then treated with the post-annealing process to create numerous air-pockets in the Ag film, forming a hierarchical Ag nanostructures. The resulting substrate obtained Cassie's wetting property with a water contact angle of 151°. Compared to the normal hydrophobic Ag nanoparticle substrate, increase of about 4.25-fold higher SERS signal was obtained for 7 μL of rhodamine 6G aqueous solutions.