Plasma-enhanced Atomic Layer Deposition Film Research Articles

(Invited) Role of Oxidant Gas for Atomic Layer Deposition of HfxZr1−XO2 Thin Films on Ferroelectricity of Metal-Ferroelectric-Metal Capacitors

We fabricated 400°C-annealed TiN/HfxZr1−xO2 (HZO)/TiN metal–ferroelectric–metal (MFM) capacitors using H2O and O2 plasma as oxidant gases of thermal (TH) and plasma-enhanced atomic layer deposition (PE-ALD), respectively, for HZO films. The PE-ALD film formed a more ferroelectric orthorhombic phase compared with the TH-ALD case. Therefore, the MFM capacitor with the PE-ALD film showed higher remanent polarization and dielectric constant. For the PE-ALD case, moreover, an oxygen-rich interfacial layer (O-rich-IL) was formed between the HZO film and TiN-bottom electrode during the ALD process. Thus, the MFM capacitor with the PE-ALD film showed less degradation of switching polarization during field cycling compared with the TH-ALD case, because an O-rich-IL should prevent the interface reaction and formation of additional oxygen vacancies in the PE-ALD film during field cycling. Based on these results, it is important to consider the selection of an ALD oxidant gas for the fabrication of HZO-based MFM capacitors.

Suppressing substrate oxidation during plasma-enhanced atomic layer deposition on semiconductor surfaces

Plasma-enhanced atomic layer deposition (PE-ALD) is widely employed in microelectronics, energy, and sensing applications. Typically, PE-ALD processes for metal oxides utilize remote inductively coupled plasmas operated at powers of >200 W, ensuring a sufficient flux of oxygen radicals to the growth surface. However, this approach often leads to significant oxidation of chemically sensitive substrates, including most technological semiconductors. Here, we demonstrate that plasma powers as low as 5 W can effectively suppress substrate oxidation while maintaining the structural, optical, and electronic quality of the films. Specifically, we investigate the growth of titanium oxide (TiOx) using two commonly used metalorganic precursors, titanium isopropoxide and tetrakis(dimethylamino)titanium. Films deposited with 5 and 300 W oxygen plasma power are nearly indiscernible from one another, exhibiting significantly lower defect concentrations than those obtained from thermal ALD with H2O. The low plasma power process preserves desired physical characteristics of PE-ALD films, including large optical constants (n > 2.45 at 589 nm), negligible defect-induced sub-bandgap optical absorption (α < 102 cm−1), and high electrical resistivity (>105 Ω cm). Similar behavior, including suppressed interface oxidation and low defect content, is observed on both Si and InP substrates. As an example application of this approach, the assessment of InP/TiOx photocathodes and Si/TiOx photoanodes reveals a significant improvement in the photocurrent onset potential in both cases, enabled by suppressed substrate oxidation during low power PE-ALD. Overall, low power PE-ALD represents a generally applicable strategy for producing high quality metal oxide thin films while minimizing detrimental substrate reactions.

High field dielectric response in κ-Ga2O3 films

κ-Ga2O3 has been predicted to be a potential ferroelectric material. In this work, undoped Ga2O3 films were grown by either plasma-enhanced atomic layer deposition (PEALD) or metal organic chemical vapor deposition (MOCVD) on platinized sapphire substrates. 50 nm thick PEALD films with a mixture of κ-Ga2O3 and β-Ga2O3 had a relative permittivity of ∼27, a loss tangent below 2%, and high electrical resistivity up to ∼1.5 MV/cm. 700 nm thick MOCVD films with predominantly the κ-Ga2O3 phase had relative permittivities of ∼18 and a loss tangent of 1% at 10 kHz. Neither film showed compelling evidence for ferroelectricity measured at fields up to 1.5 MV/cm, even after hundreds of cycles. Piezoresponse force microscopy measurements on bare κ-Ga2O3 showed a finite piezoelectric response that could not be reoriented for electric fields up to 1.33 MV/cm.

Comparative Study of Thermal and Plasma-Enhanced Atomic Layer Deposition of Iron Oxide Using Bis(N,N'-di-butylacetamidinato)iron(II).

Only a few iron precursors that can be used in the atomic layer deposition (ALD) of iron oxides have been examined thus far. This study aimed to compare the various properties of FeOx thin films deposited using thermal ALD and plasma-enhanced ALD (PEALD) and to evaluate the advantages and disadvantages of using bis(N,N'-di-butylacetamidinato)iron(II) as an Fe precursor in FeOx ALD. The PEALD of FeOx films using iron bisamidinate has not yet been reported. Compared with thermal ALD films, PEALD films exhibited improved properties in terms of surface roughness, film density, and crystallinity after they were annealed in air at 500 °C. The annealed films, which had thicknesses exceeding ~ 9 nm, exhibited hematite crystal structures. Additionally, the conformality of the ALD-grown films was examined using trench-structured wafers with different aspect ratios.

Exploring argon plasma effect on ferroelectric Hf0.5Zr0.5O2 thin film atomic layer deposition

The doped/alloyed HfO2 and ZrO2 thin films revolutionized not only the field of ferroelectric physics but also various ranges of device applications. Especially when the two oxides are combined in an 1:1 ratio, the ferroelectric polarization of the material became the most distinctive. Many researchers have investigated various different process conditions such as controlling Hf0.5Zr0.5O2 (HZO) film thickness and modifying different metal electrodes. Here, we explored the effect of additional Ar plasma treatment to the HZO film. The additional Ar plasma was exposed to the plasma-enhanced atomic layer deposition (PEALD) HZO for this study. Then, the sample was compared with a conventional PEALD and thermal ALD HZO films. By understanding the polarization–electric field (P–E), current–electric field (I–E), and electrical breakdown characteristics of the different samples, it was found that the Ar plasma treatment can control the degree of ferroelectric and antiferroelectric phases of HZO film.

Resolving self-limiting growth in silicon nitride plasma enhanced atomic layer deposition with tris-dimethylamino silane precursor

Self-limiting character of the involved surface reactions is essential for highly uniform and conformal growth in atomic layer deposition (ALD). However, the poor conformal coverage (<75%) that is often reported with silicon nitride (SiNx) plasma enhanced ALD (PEALD) processes using metalorganic Si-precursors is confounding. In this article, we report our study of the SiNx PEALD process using the tris-dimethylamino silane (3DMAS) precursor and forming gas (5% H2–95% N2) reactant plasma. For the substrate temperature (Tsub) range of 50 °C ≤ Tsub ≤ 150 °C, growth per cycle (GPC) for SiNx deposition was found to approach saturation at 0.034 ± 0.001 nm/cycle though higher Tsub required longer 3DMAS exposures (tA) for saturation. However, for Tsub > 150 °C, SiNx GPC was seen to increase with tA, indicating nonself-limiting growth from potential chemical vapor deposition-like side reactions emerging at higher temperatures. The refractive index (n) of 2.097 ± 0.003 at 2 eV with an optical bandgap of ∼1.7 eV determined from in situ spectroscopic ellipsometry measurements, and peaks s1 and n1 with ΔBE = 295.42 eV in Si2p and N1s XPS spectra measured on the capped SiNx sample were found to agree with the optical constants and chemical characteristics reported for the silicon nitride material. SiNx films deposited at Tsub = 250 °C (nonself-limiting) were found to be more resistant to ambient oxidation as compared to SiNx PEALD films grown at Tsub = 100 °C. Although an entire 30 nm thick SiNx PEALD film was oxidized after an unavoidable long ambient exposure, a cross-sectional transmission electron microscope image showed a conformal coverage of 95%–98% in a 3D trench structure with an aspect ratio of 4.5. Furthermore, higher resistance to ambient oxidation in plasma treated of SiNx PEALD films demonstrates a potential of postgrowth treatments to improve desirable material properties without resorting to high-temperature processes.

Continuous polymer films deposited on top of porous substrates using plasma-enhanced atomic layer deposition and molecular layer deposition

Molecular layer deposition (MLD) is able to produce ultrathin polymer films with control over thickness, cross-linking, and chemical composition. With these capabilities, MLD should be useful in the fabrication of novel polymer membranes on porous supports. However, confining a continuous MLD film to the surface of porous substrates is difficult because of MLD film growth in the pores. The deposition in the pores lowers the conductance of the porous support. This paper presents a method to deposit continuous polymer films on top of porous substrates. In this method, Al2O3 plasma-enhanced atomic layer deposition (PE-ALD) using trimethylaluminum and oxygen plasma as the reactants was first used to cap the pores of the substrate. Subsequently, a polyamide MLD film was deposited on the Al2O3 PE-ALD capping layer using m-phenylenediamine and trimesoyl chloride as the reactants. The Al2O3 pore caps were then removed from the porous substrate by etching from the backside using a timed exposure to a dilute sodium hydroxide solution. This method was demonstrated using anodic aluminum oxide (AAO) and polyethersulfone (PES) porous substrates. Al2O3 PE-ALD film growth was limited to the top of the porous substrate, resulting in rapid surface recombination or high sticking coefficients for the reactive plasma species within the pores. Gas permeance measurements confirmed the pore capping of the AAO substrates. The reopening of the pores by dissolving the Al2O3 pore caps with a sodium hydroxide solution was monitored using gas permeance versus etch time. The removal of the Al2O3 pore caps from the PES substrates could also dissolve the Al2O3 layer underneath the MLD film. The loss of this Al2O3 layer led to the detachment of the MLD film from the PES substrate. However, the MLD film could be anchored to the PES support at fractures located in the Al2O3 film prior to the MLD. The Al2O3 film fracture allowed the MLD film to anchor firmly to the PES substrate by MLD in the pores of the PES porous substrate. The distance between the anchor points was a function of fracture density. This distance could be controlled by applying a tensile stress to the Al2O3 PE-ALD film to fracture the film through sample bending. This method produced firmly anchored polymer MLD films on top of the PES porous substrates.

Tetraallyltin precursor for plasma enhanced atomic layer deposition of tin oxide: Growth study and material characterization

In this letter, the authors report on the application of tetraallyltin (TASn) as an Sn-precursor for plasma enhanced atomic layer deposition (PEALD) of tin oxide (SnO2) thin films. The selection procedure for the TASn precursor is discussed. Tin oxide PEALD growth is shown to be self-limiting with a constant growth-per-cycle of 0.046 ± 0.002 nm/cycle in the substrate temperature (Tsub) range of 50–150 °C. Optical constants, chemical bonding, and electronic properties of as-grown PEALD films were characterized to evaluate the quality of tin oxide film obtained with the TASn precursor. A 21.6 nm tin oxide film grown at Tsub = 50 °C exhibited an indirect optical bandgap (Eg) of 2.94 eV and appeared amorphous from the glancing incidence x-ray diffraction pattern. Binding energy difference ΔBE(O1s, Sn3d5/2) = 43.77 eV and valence band emission in x-ray photoelectron spectroscopy showed that these were near-stoichiometric SnO2 with the relative O:Sn atomic ratio of 1.98 (or SnO1.98). Moreover, room temperature electrical resistivity ρele = 13.1 ± 1.6 mΩ cm, with electron concentration Ne = (3.78 ± 0.79) × 1019 cm−3 and Hall mobility μe = 13.2 ± 2.0 cm2 V−1 s−1, showed that electrical characteristics of the as-grown tin oxide films with the TASn precursor are comparable to those grown using other standard Sn precursors.

Comparisons of alumina barrier films deposited by thermal and plasma atomic layer deposition

Barrier films are commonly deposited onto flexible substrates by atomic layer deposition (ALD) to protect organic electronics from degradation due to the ingress of moisture. Both thermal ALD and plasma-enhanced ALD (PEALD) have been used for this purpose, but few comparisons have been made as to which technique produces superior barrier films. In this study, alumina (Al2O3) barrier films have been deposited by thermal ALD and PEALD to investigate the effect of the deposition technique on the water vapor transmission rate (WVTR). Al2O3 films with thicknesses of approximately 10 or 20 nm were deposited at 100 or 120°C. The chemistry, morphology, and density of the films were investigated with X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray reflectometry respectively. The WVTRs of the films were measured using tritiated water (HTO) permeation at 25°C and 95% relative humidity. Both the thermal and PEALD films had similar Al:O ratios, whereas the PEALD films were slightly smoother than the thermal ALD films. No significant difference in the film densities was observed. All PEALD films had lower WVTRs than their thermally deposited counterparts. The lowest WVTR measured was 4.2 × 10−2 g m−2/day for a 17-nm-thick PEALD Al2O3 film deposited at 120°C. These results indicate the importance of optimizing deposition parameters to enable production of the most effective barrier films, which are essential in applications such as organic electronics.

Comparison of mechanical properties and composition of magnetron sputter and plasma enhanced atomic layer deposition aluminum nitride films

A comparative study of mechanical properties and elemental and structural composition was made for aluminum nitride thin films deposited with reactive magnetron sputtering and plasma enhanced atomic layer deposition (PEALD). The sputtered films were deposited on Si (100), Mo (110), and Al (111) oriented substrates to study the effect of substrate texture on film properties. For the PEALD trimethylaluminum–ammonia films, the effects of process parameters, such as temperature, bias voltage, and plasma gas (ammonia versus N2/H2), on the AlN properties were studied. All the AlN films had a nominal thickness of 100 nm. Time-of-flight elastic recoil detection analysis showed the sputtered films to have lower impurity concentration with an Al/N ratio of 0.95, while the Al/N ratio for the PEALD films was 0.81–0.90. The mass densities were ∼3.10 and ∼2.70 g/cm3 for sputtered and PEALD AlN, respectively. The sputtered films were found to have higher degrees of preferential crystallinity, whereas the PEALD films were more polycrystalline as determined by x-ray diffraction. Nanoindentation experiments showed the elastic modulus and hardness to be 250 and 22 GPa, respectively, for sputtered AlN on the (110) substrate, whereas with PEALD AlN, values of 180 and 19 GPa, respectively, were obtained. The sputtered films were under tensile residual stress (61–421 MPa), whereas the PEALD films had a residual stress ranging from tensile to compressive (846 to −47 MPa), and high plasma bias resulted in compressive films. The adhesion of both films was good on Si, although sputtered films showed more inconsistent critical load behavior. Also, the substrate underneath the sputtered AlN did not withstand high wear forces as with the PEALD AlN. The coefficient of friction was determined to be ∼0.2 for both AlN types, and their wear characteristics were almost identical.

Optical in situ monitoring of plasma-enhanced atomic layer deposition process

An optical in situ process monitoring method for the early detection of anomalies in plasma process equipment is presented. Cyclic process steps of precursor treatment and plasma reaction for the deposition of an angstrom-scale film increase their complexity to ensure the process quality. However, a small deviation in process parameters, for instance, gas flow rate, process temperature, or RF power, may jeopardize the deposited film quality. As a test vehicle for the process monitoring, we have investigated the aluminum-oxide (Al2O3) encapsulation process in plasma-enhanced atomic layer deposition (PEALD) to form a moisture and oxygen diffusion barrier in organic-light emitting diodes (OLEDs). By optical in situ monitoring, we successfully identified the reduction in oxygen flow rates in the reaction steps, which resulted in a 2.67 times increase in the water vapor transmission ratio (WVTR) of the deposited Al2O3 films. Therefore, we are convinced that the suggested in situ monitoring method is useful for the detection of process shifts or drifts that adversely affect PEALD film quality.

Aluminum nitride thin films deposited by hydrogen plasma enhanced and thermal atomic layer deposition

Plasma enhanced atomic layer deposition (PE-ALD) of aluminum nitride (AlN) thin films often utilizes NH3 or a mixture of N2 and H2 as a plasma source. However, the possibility of separating the activation step from the nitridation step by using H2 alone as the plasma source has never been explored. In this paper, we study the deposition of AlN by PE-ALD by using trimethylaluminum, H2 plasma and NH3 for deposition temperatures below 400 °C. The self-limiting ALD growth was achieved between 325 °C and 350 °C. As a comparison, AlN was also deposited by thermal ALD (T-ALD), where surface reactions between TMA and NH3 occurred with reasonable growth rates only at temperatures above 400 °C. The PE-ALD films showed low oxygen (1.5 at.%) and carbon contaminations (1 at.%). The T-ALD films contained carbon (5 at.%) mainly attributed to the presence of CAl bonds that was insignificant in PE-ALD films. The flow rate of H2 used in H2 plasma was found to have a significant impact on the preferred orientation of AlN films, where higher H2 flow rate promoted the (002) preferred orientation. Besides, the electrical resistivities were probed to be 108 Ω cm, as expected in an insulating material.As an example, AlN was used to infiltrate porous sintered silicon carbide (SiC). Both AlN deposited by PE-ALD and by T-ALD operating with exposure mode deposited at 400 °C were attempted. Even though, there is a greater risk for TMA precursor to decompose at 400 °C, infiltration of AlN was more successful by T-ALD operating with exposure mode.

A combinatorial approach to enhance barrier properties of thin films on polymers: Seeding and capping of PECVD thin films by PEALD

A combinatorial approach to deposit gas barrier layers (GBLs) on polyethylene terephthalate (PET) by means of plasma‐enhanced chemical vapor deposition (PECVD) and plasma‐enhanced atomic layer deposition (PEALD) is presented. Thin films of SiOx and SiOxCyHz obtained from PECVD were grown either subsequently on a PEALD seeding layer (SiO2) or were capped by ultrathin PEALD films of Al2O3 or SiO2. To study the impact of PEALD layers on the overall GBL performance, PECVD coatings with high macro defect densities and low barrier efficiency with regard to the oxygen transmission rate (OTR) were chosen. PEALD seeding layers demonstrated the ability to influence the subsequent PECVD growth in terms of the lower macro defect density (9 macro‐defects mm−2) and improved barrier performance (OTR = 0.8 cm3 m−2 day−1), while the PEALD capping‐route produced GBLs free of macro‐defects.

Plasma-enhanced atomic layer deposition of nickel thin film using bis(1,4-diisopropyl-1,4-diazabutadiene)nickel

The authors report the plasma enhanced atomic layer deposition (PEALD) of a nickel thin film using bis(1,4-diisopropyl-1,4-diazabutadiene)nickel [Ni(dpdab)2] and NH3 plasma. Ni(dpdab)2 is an oxygen-free liquid Ni precursor with a vapor pressure of 0.23 Torr at 80 °C. Ni films were deposited by alternating exposures to Ni(dpdab)2 and NH3 plasma at 125–250 °C. Ni(dpdab)2 showed the atomic layer deposition (ALD) process window between 125 and 150 °C with the ALD growth of ∼2 Å/cycle. The growth rate increased significantly above 200 °C, probably due to the thermal decomposition of the Ni precursor. The resistivity of the ALD thin film decreased with increasing radio-frequency (RF) power, and lower resistivities with high RF powers are due to the lower carbon concentration and larger grain size. The minimum resistivity of the PEALD film at 150 °C in the ALD process window was 146 μΩ cm, which is significantly higher than bulk Ni resistivity (7.0 μΩ cm) mainly due to the nitrogen content (∼13%) in the as-deposited film. For a lower nitrogen concentration, the PEALD film was annealed at 400 °C under 1 Torr of H2 for 30 min, resulting in the reduction of resistivity from 146 to 13.3 μΩ cm and removal of nitrogen impurities.

Comparative study on growth characteristics and electrical properties of ZrO2 films grown using pulsed plasma-enhanced chemical vapor deposition and plasma-enhanced atomic layer deposition for oxide thin film transistors

The deposition of high-quality ZrO2 films has been achieved using both pulsed plasma-enhanced chemical vapor deposition (P-PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) with (C5H5)Zr[N(CH3)2]3 as a Zr precursor. The authors compared the growth characteristics, chemical compositions, and electrical properties of P-PE-CVD and PE-ALD ZrO2 prepared under various deposition conditions. The ZrO2 films prepared using both methods showed high purity and good stoichiometry. Electrical characterization of a metal-oxide-semiconductor capacitor utilizing the ZrO2 films showed that PE-ALD films have a relatively lower leakage current than P-PE-CVD films, whereas the dielectric constant, interface trap density, and hysteresis of both films are similar. Applying both methods, the electrical properties of ZrO2 films were also evaluated using In–Ga–Zn–O thin-film transistors (TFTs), which showed a good device performance in terms of high Ion-Ioff ratios (>108) and low off-currents (<10−11 A). In addition, ZrO2-based TFT showed high reliability against a negative Vth shift. Based on the self-limiting growth characteristics and electrical properties of P-PE-CVD, the authors found that the P-PE-CVD process results in electrical properties comparable to those of PE-ALD ZrO2 films. Thus, the authors believe that P-PE-CVD can be an alternative process to PE-ALD for future electronic device applications, especially for display applications due to its good electrical properties with high throughput.

The α and γ plasma modes in plasma-enhanced atomic layer deposition with O2–N2 capacitive discharges

Two distinguishable plasma modes in the O2–N2 radio frequency capacitively coupled plasma (CCP) used in remote plasma-enhanced atomic layer deposition (PEALD) were observed. Optical emission spectroscopy and spectra interpretation with rate coefficient analysis of the relevant processes were used to connect the detected modes to the α and γ modes of the CCP discharge. To investigate the effect of the plasma modes on the PEALD film growth, ZnO and TiO2 films were deposited using both modes and compared to the films deposited using direct plasma. The growth rate, thickness uniformity, elemental composition, and crystallinity of the films were found to correlate with the deposition mode. In remote CCP operations the transition to the γ mode can result in a parasitic discharge leading to uncontrollable film growth and thus limit the operation parameters of the capacitive discharge in the PEALD applications.

Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using a Novel Silylamine Precursor.

We report the plasma-enhanced atomic layer deposition (PEALD) of silicon nitride thin film using a silylamine compound as the silicon precursor. A series of silylamine compounds were designed by replacing SiH3 groups in trisilylamine by dimethylaminomethylsilyl or trimethylsilyl groups to obtain sufficient thermal stability. The silylamine compounds were synthesized through redistribution, amino-substitution, lithiation, and silylation reactions. Among them, bis(dimethylaminomethylsilyl)trimethylsilyl amine (C9H29N3Si3, DTDN2-H2) was selected as the silicon precursor because of the lowest bond dissociation energy and sufficient vapor pressures. The energies for adsorption and reaction of DTDN2-H2 with the silicon nitride surface were also calculated by density functional theory. PEALD silicon nitride thin films were prepared using DTDN2-H2 and N2 plasma. The PEALD process window was between 250 and 400 °C with a growth rate of 0.36 Å/cycle. The best film quality was obtained at 400 °C with a RF power of 100 W. The PEALD film prepared showed good bottom and sidewall coverages of ∼80% and ∼73%, respectively, on a trench-patterned wafer with an aspect ratio of 5.5.

Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study

The process parameters' impact of the plasma-enhanced atomic layer deposition (PE-ALD) method on the oxygen to nitrogen (O/N) ratio in titanium oxynitride (TiOxNy) films was studied. Titanium(IV)isopropoxide in combination with NH3 plasma and tetrakis(dimethylamino)titanium by applying N2 plasma processes were investigated. Samples were characterized by the in situ spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization (current–voltage: I-V and capacitance–voltage: C-V) methods. The O/N ratio in the TiOxNy films is found to be very sensitive for their electric properties such as conductivity, dielectric breakdown, and permittivity. Our results indicate that these PE-ALD film properties can be tuned, via the O/N ratio, by the selection of the process parameters and precursor/coreactant combination.

Influence of atomic layer deposition valve temperature on ZrN plasma enhanced atomic layer deposition growth

Atomic layer deposition (ALD) relies on a sequence of self-limiting surface reactions for thin film growth. The effect of non-ALD side reactions, from insufficient purging between pulses and from precursor self-decomposition, on film growth is well known. In this article, precursor condensation within an ALD valve is described, and the effect of the continuous precursor source from condensate evaporation on ALD growth is discussed. The influence of the ALD valve temperature on growth and electrical resistivity of ZrN plasma enhanced ALD (PEALD) films is reported. Increasing ALD valve temperature from 75 to 95 °C, with other process parameters being identical, decreased both the growth per cycle and electrical resistivity (ρ) of ZrN PEALD films from 0.10 to 0.07 nm/cycle and from 560 to 350 μΩ cm, respectively. Our results show that the non-ALD growth resulting from condensate accumulation is eliminated at valve temperatures close to the pressure corrected boiling point of precursor.

Self Assembled Metamaterials Formed via Plasma Enhanced ALD of Ag Thin Films

Plasma enhanced atomic layer deposition (PEALD) of Ag thin films using Ag(fod)(PEt3) as the precursor has been investigated. Although a regular film of Ag does not have any plasmonic activity, when silver is grown by PEALD, it exhibits unexpected plasmonic behavior, shown in Fig.1 characterized by the Surface Enhanced Raman (SERS) intensity. We show that these films consist of a mosaic structure (inset, Fig. 1) characterized by 2D Ag islands separated by very narrow air gaps (<8nm), which are parallel and extend down to the substrate. These parallel air gaps are an inherent property of the PEALD film, and the source of the plasmonic behavior. We have modeled the ALD-Ag film using FDTD E-M simulations, representing the film as a ring shaped air gap in Ag. The result of the model is shown in figure 2 where we display spatial maps of the electric fields at the resonance wavelength above the film and in cross section. The maps show a very strong confinement of optical fields in the gaps with an enhancement >10x. When PEALD Ag is combined with an active SERS material, such as dielectric core nanowires, the SERS enhancement can be enhanced by > 100x. We have also calculated the time evolution of these fields and have found that the confined plasmonic fields persist long after the excitation pulse. These results indicate that the ALD-Ag is a metamaterial with unique optical constants. Since the air gaps are critical to the plasmonic behavior of this material, we will also discuss the effect of surface modification of the Ag PEALD. This was achieved by examining the effect of Ag oxide removal by H2 plasma as well as by ALD deposition of Al2O3, where the conformal nature of the coverage is critical. Ellipsometry data indicate a blue shift of the plasmonic resonance with the widening of the air gap (achieved by oxide removal) and with the addition of 2 cycles of Al2O3, which result in the lowering of the refractive index with the addition of the Al2O3. We will discuss the source of this blue shift and show how ellipsometry combined with electric field simulations can be used to obtain detailed chemical information on the surface and in the air gaps of this material, which would not be possible by experiment alone.