1 Introduction

Metal films on organic substrates, encompassing polymers, fabrics, textiles, and more, have garnered substantial research attention due to their diverse applications. Nonetheless, achieving robust adhesion between metal films and organic materials remains a formidable challenge, necessitating innovative solutions. This challenge has spurred extensive research endeavors, as evidenced by recent investigations [1, 2]. The weak adhesion can be attributed to two key factors: the non-polar nature of most organic surfaces resulting in low surface energy and poor hydrophilicity, as well as the significant disparity in adhesion energies between metals and organic materials. To address this issue, a range of methodologies have been explored, including plasma etching, [3, 4] acid and solution etching [5, 6], the introduction of oxide strengthening layers [7], sputtering etching [8], and ultraviolet (UV)/ozone treatment in equipment chambers [9,10,11]. While these methods prove effective, they come with inherent limitations, particularly concerning large-scale applications. A straightforward and cost-effective method for modifying extensive organic surfaces is imperative. Our focus has turned to the UV/ozone method due to its simplicity and one-step process, setting it apart from other techniques. Notably, UV/ozone treatments have mainly been confined to UV-ozone chambers, restricting their application for modifying substantial surfaces. For instance, Liu et al. [10], TSAO et al. [12], Retolaza et al. [11], Song et al. [13], and Hamdi et al. [14] utilized commercial UV-ozone systems for the modification of surfaces. Inspired by ozone generation mechanisms and the application of UV light in ozone cleaners, we come up an idea of solely using a UV light lamp for surface modification in open space. The feasibility of this approach, its effectiveness in resolving adhesion issues, and its potential scalability to substantial surfaces warrant thorough investigation.

Transparent conducting films have found diverse applications, including transparent electrodes for solar cells, display screens, and electromagnetic interference (EMI) shielding. EMI shielding is of paramount importance in diverse applications that necessitate protection against electromagnetic interference or disruption of electronic and communication device operations, including aircraft stealth technology. As an illustration, for cabin canopy electromagnetic shielding films, achieving both visible light transmittance performance and electromagnetic shielding efficiency in the S (2–4 GHz), C (4–8 GHz), X (8–12 GHz), and Ku (12–18 GHz) bands is crucial. Striking a balance between a clear field of vision and effective reduction of external electromagnetic radiation interference on aircraft internal electronic devices necessitates achieving a transmittance of about 70% and an electromagnetic shielding efficiency of -20 dB. Remarkably, these two objectives stand in stark contrast. Electromagnetic shielding capabilities are exclusive to conductive materials, prompting the need to reconcile transparency, chemical stability, and other factors. Transparent conductive films encompass a range of materials, including transparent conducting wide-gap inorganic films (e.g., ITO), conductive polymers, graphene and carbon nanotubes, metal meshes and metal nanowire networks, and thin metal films [15]. Although ITO offers high conductivity and transparency, its application on most polymers is constrained by the high processing temperature due to inherent drawbacks [16]. Other transparent films offer benefits but also pose challenges when applied to organic substrates [15]. Films made of metal meshes, nanotubes, and nanowires possess rough surfaces and uneven conductance within the films. Metal films composed of materials like Ag and Au exhibit remarkable conductivity (~ 106 S·cm−1), making them promising candidates for applications that necessitate both electrical and thermal conductivity. In particular, Au stands out as the most stable metal, suitable for diverse applications without concerns about film degradation. However, achieving optimal adhesion, transparency, and conductivity remains a persistent challenge. Therefore, a systematic study of depositing an ultrathin Au film that maintains transparency to visible light while exhibiting high electromagnetic interference (EMI) shielding capability is needed.

This paper embarks on two pivotal objectives. Firstly, an open-space UV light illumination method as a straightforward and economical approach to modify PMMA surfaces and enhance adhesion is proposed and explored. While the primary focus lies on PMMA, this approach holds promise for modifying various organic surfaces. The adaptability of this method for surfaces of diverse sizes, shapes, and locations presents a significant advantage. Various aspects such as surface morphology, roughness, water contact angle, and functional group analysis of PMMA surfaces treated for different durations are encompassed in this investigation. The adhesion between modified PMMA substrate and Au film is assessed, followed by an analysis of the underlying modification mechanism. The ultrathin Au films coated on PMMA surfaces are transparent to visible light and exhibit exceptional electromagnetic interference (EMI) shielding efficiency, making them suitable for applications such as EMI shielding windows and aerospace visualization systems. Overall, this work advances a novel, cost-effective approach for large-scale surface modification in open space, and a systematic study of the properties of ultrathin Au films deposited on modified PMMA surfaces.

1.1 Experimental

For our experimental methodology, a 36W Philips low-pressure mercury lamp capable of emitting UV light at 185 nm and 254 nm is employed. Prior to loading, the PMMA samples underwent ultrasonic cleaning in deionized water for 5–10 min. The UV lamp was preheated by turning it on for a few minutes before being turned off. Subsequently, the PMMA samples were positioned beneath the UV light and exposed for varying durations, specifically 0 min, 5 min, 10 min, 20 min, 30 min, and 60 min. After the UV treatment, the samples were left in the air for approximately 10 min before conducting measurements.

The deposition of the Au film was carried out using magnetron sputtering. The power applied to the Au target during deposition was 40 W. To determine the deposition rate, an initial thick Au film was coated on the samples, revealing a rate of 0.45 nm/s on PMMA substrates treated with UV light for 30 min. Subsequently, for the deposition of ultrathin films, varying deposition durations of 0 s, 15 s, 25 s, 35 s, and 60 s were utilized, corresponding to Au film thicknesses of 0 nm, 7 nm, 11 nm, 15 nm, and 27 nm, respectively.

Several analytical techniques were employed to assess the UV-treated PMMA samples and Au/PMMA samples. The Biolin Scientific Theta Lite optical tensiometer was used to measure the contact angle of water droplets on PMMA surfaces before and after UV illumination. Film thickness measurements were conducted using the Bruker DekatakXT stylus profilometer. For surface morphology visualization, the Bruker atomic force microscope (AFM) was utilized. The Thermo Fisher Scientific Nicolet attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was utilized to analyze PMMA surfaces prior to and following UV light illumination treatment. Finally, the electromagnetic interference shielding efficiency or attenuation for vertical wave illumination within the 2–18 GHz range was measured using the Keysight Technologies N5234A microwave network analyzer.

2 Results and discussion

Polymethyl methacrylate (PMMA) stands as a widely utilized highly transparent organic glass in numerous critical applications, encompassing skylights, aircraft windows and canopies. However, the adhesion between a metal film and an unmodified polymer, such as PMMA, is inherently weak, often resulting in the detachment of the film. Addressing this adhesion issue is imperative, particularly for achieving a robust Au film on a large PMMA surface. This study introduces and investigates a straightforward and cost-effective open-space method for modifying PMMA surfaces. The proposed method involves illuminating the polymer surface with a conventional UV lamp capable of emitting 185 nm and 254 nm UV lights. A 185 nm UV light, possessing a photon energy of 647 kJ.mol−1, has been proven to produce ozone (O3) effectively. On the other hand, the 254 nm UV light with a photon energy of 427 kJ.mol−1 is an optimal wavelength to target various bonds of polymers. These wavelengths encompass energies surpassing the majority of bonding energies of various bonds illustrated in Table 1. With a focus on develo** an economical approach, we chose a cost-effective conventional low-power (36 W) Philips lamp. The lamp was affixed to a table, and the distance between the lamp and the samples was adjusted to approximately 5 cm. Notably, the UV treatment was conducted in an open space without the use of chambers or enclosure boxes. Therefore, this approach exhibits scalability, allowing the treatment of extensive surface areas by incorporating multiple lamps into arrays.

Table 1 Chemical molecule binding energy [16, 17]
Full size table

The alterations in the surface morphology of PMMA resulting from the illumination of a Philips 36W dual-wavelength (185 nm and 254 nm) ultraviolet lamp for varying durations—0 min, 5 min, 10 min, 20 min, 30 min, and 60 min—are presented in Fig. 1. The AFM surface topography of unilluminated PMMA is depicted in Fig. 1(a), while Fig. 1(b-f) showcase the topography images of PMMA surfaces after distinct UV illumination periods. Evidently, the unilluminated PMMA surface exhibits raised pits, potentially arising from the alignment of long molecular chains within the organic polymer. The roughness of this surface is measured at 1.19 nm. Following a 5-min UV illumination, the surface morphology undergoes significant changes, and the roughness is increased to 1.33 nm. With 10 min of UV exposure, islands become apparent, leading to a further increase in roughness to 1.84 nm due to chemical modifications occurring on the surface. Subsequently, a transition to a relatively flat surface occurs after the 10-min mark, causing a reduction in roughness from 1.84 nm (10 min) to 1.34 nm (20 min), 0.91 nm (30 min), and 0.34 nm (60 min). This reduction is attributed to processes such as oxidation, degradation, and polymer chain fracture. It is worth noting that the surfaces exhibiting lower roughness levels display numerous nanopores, possibly formed through the oxidation and rearrangement of polymer chains due to prolonged UV irradiation in an air environment.

Fig. 1
figure 1

AFM images showing surface morphology of the PMMA treated with UV illumination for different durations: a 0 min, b 5 min, c 10 min, d 20 min, e 30 min and f 60 min. Rq is the roughness

Full size image

This open-space UV illumination approach offers a potential means to modify PMMA surfaces effectively, as evident from the notable changes observed in surface morphology. However, a deeper understanding of the underlying mechanisms and their implications for adhesion enhancement is crucial, which will be further discussed.

To investigate the impact of 36 W ultraviolet (UV) light illumination on the surface free energy, adhesion, and wetting properties of PMMA surfaces, contact angle experiments were conducted using the Theta Lite optical contact angle measuring system. The results of these experiments are displayed in Fig. 2, illustrating images and contact angles of deionized water drops on the UV-illuminated PMMA surfaces. Two contact angles for each water drop are measured, and the average of these angles is provided in the figure caption.

Fig. 2
figure 2

Measurement diagram of water drops on PMMA samples modified by different durations of UV light illumination. Two contact angles were measured for each water drop as seen, and the average of these two angles for each UV illumination duration are a 82.7°for 0 min, b 66.8°for 5 min, c 54.2°for 10 min, d 27.7°for 20 min, e 24.8°for 30 min and f 21.9°for 60 min

Full size image

The unmodified PMMA surface exhibits a contact angle of 82.7°, closely aligning with the reported water contact angle of 80.3° for PMMA substrates in existing literature [12]. This high contact angle is due to the hydrophobic nature of the virgin PMMA surface. In this hydrophobic state, oxygen atoms within the chemical structure of PMMA (C5H8O2)n are predominantly bonded within the material, making it challenging to form strong chemical bonds with external metal atoms due to the low surface binding forces.

Figure 2(b-f) illustrate a reduction in water contact angle as the duration of UV light illumination on PMMA increases. Notably, the contact angle of water drop on PMMA surface decreases significantly from 82.7° (0 min UV illumination) to 66.8° (5 min), 54.2° (10 min), 27.7° (20 min), experiences a rapid decrease from 82.7° to 27.7° within only 20 min of UV illumination, followed by a very slow decrease with further UV exposure (see Fig. 3). A small contact angle or high surface energy suggests high wettability and surface hydrophilicity, favoring increased adhesion of deposited films to the substrate. The great enhancement of PMMA surface hydrophilicity with only 20 min UV illumination indicates that our proposed UV light illumination approach can effectively alter PMMA surface energy. Notably, this treatment duration is comparable to those of UV-ozone chamber treatments in literature [13, 14, 18]. The increase in hydrophilicity is typically attributed to the augmentation in the presence of oxygen-containing functional groups such as hydroxyl, carboxyl, and carbonyl groups on the modified PMMA surface [19], an aspect that will be analyzed in greater depth through Fourier infrared spectroscopy below.

Fig. 3
figure 3

The contact angles for water drops on UV treated PMMA samples as a function of UV illumination duration

Full size image

To gain a deeper insight into the modified PMMA surface, attenuated total reflection Fourier infrared spectroscopy (ATR-FTIR) is employed to qualitatively analyze the chemical bonds and functional groups before and after UV illumination. Since PMMA becomes opaque in the infrared spectrum beyond a wavelength of 2500 nm (wavenumber < 4000), conventional transmission mode FTIR measurements are unsuitable. Consequently, reflection mode FTIR, specifically ATR-FTIR, is utilized to assess the chemical bond structure and functional group composition on the PMMA surface. While FTIR spectroscopy provides qualitative analysis of chemical composition changes, it does not provide quantitative data regarding the extent of change.

For the ATR-FTIR analysis, the unmodified PMMA and the PMMA modified by 30 min of UV light illumination are selected, with the results displayed in Fig. 4. From this disparity, the appearance of an absorption band in the range of 2800–3650 cm−1 originates from the expansion vibration of C-H, with weakened C-H telescopic vibration peaks at 2990 cm−1 and 2950 cm−1, signifying oxidation of methyl or methylene groups [19,20,21].

Fig. 4
figure 4

Attenuated Total Reflectance Infrared Spectra of PMMA Surface Before and After UV Ozone Treatment a Untreated PMMA; b PMMA modified with UV ozone for 30 min

Full size image

Moreover, increased absorption peak intensities at 1220 cm−1 and 1050–1100 cm−1 are caused by the telescopic vibration of alcohol and carboxylic acid C-O, respectively. Therefore, it can be considered that after UV illumination, alcohols and carboxylic acids are formed on the surface of PMMA. The region of 1300 ~ 1000 cm−1 is the region of ester C–O–C, and the decreased infrared absorption intensity in this region for the modified PMMA indicates an effective photodegradation and the formation of carboxylic acid [21]. The carbonyl (C = O) absorption region (1600–1800 cm−1) showcases a weakened main carbonyl peak at 1725 cm−1, signifying photodegradation of methyl methacrylate groups within the PMMA polymer, indicating side-chain methyl or methylene elimination. The entire carbonyl group absorption region is widened, reflecting the creation of new oxidized carbonyl compounds such as aldehydes, ketones, carboxylic acids, and new lipids and peroxy acids bonded to the PMMA chain. The 1740–1840 cm−1 region on the left side of the main carbonyl peak can be attributed to carboxylic acid and lipid groups. The region of 1650–1700 cm−1 on the right can be attributed to aldehydes and ketones [21].

The surface modification of organic materials is essentially driven by oxidative reactions resulting from the combined influence of ultraviolet (UV) light illumination and ozone reaction. UV/ozone modification generates reactive gaseous species, such as atomic oxygen and ozone. Atomic oxygen exists in two highly active forms: excited-state oxygen atoms and ground-state oxygen atoms [22]. Polymer molecules typically undergo reactions with atomic oxygen through the following mechanism, where these atomic oxygen species are produced in conjunction with the continuous dissociation of oxygen molecules and the generation of ozone molecules. The qualitative analysis of infrared absorption spectra demonstrates that UV illumination of PMMA results in photolysis and oxidation of main chain and side-chain methyl/methylene groups. Active oxygen radicals are generated upon absorbing UV light at 254 nm, which, combined with free radicals on the PMMA surface, yields oxygen-containing polar functional groups such as hydroxyl, carboxyl, and carbonyl groups. This enhances the surface energy and hydrophilicity.

The UV light illumination method for PMMA modification can be comprehended as follows: The selected UV lamp emits 185 nm and 254 nm waves, capable of generating ozone (O3) when the 185 nm UV light reacts with oxygen molecules (O2). Ozone is recognized for its reactivity in surface modification. Under UV illumination at 185 nm, molecular oxygen transitions to excited state molecular oxygen. This excited state oxygen then dissociates into ground state oxygen atoms, which, in turn, form ozone O3. Subsequently, UV irradiation at 254 nm decomposes ozone into atomic oxygen and molecular oxygen. Atomic oxygen is highly active and reacts with molecular oxygen, ozone, and other free radicals, leading to the formation of oxidized functional groups like carbonyl and carboxyl groups, as well as crosslinking reactions between polymer chains.

Irradiation of PMMA with UV/ozone not only elevates the polar surface energy but also amplifies the degree of oxidation, thereby inducing modifications in the surface roughness. Notably, functional groups, including carbonyl groups, carboxyl groups, and ester groups, undergo oxidation as the duration of UV irradiation increases, until PMMA surface is fully modified. The results of our experimentation advocate that UV light exposure prompts the depolymerization of polymer chains, yielding a combination of random breakages and the cleavage of side-chain methyl and methylene groups. On one hand, the resultant decomposition and oxidation of the polymer chains lead to alterations in the surface morphology and roughness of the PMMA material, thereby bolstering the mechanical adherence of subsequently applied films to the surface. On the other hand, an insightful analysis of the outcomes concerning the surface water contact angle and the absorption spectrum in the infrared domain reveals an augmentation of hydrophilic groups, notably including carboxyl, carbonyl, and hydroxyl groups, on the modified surface. This influx of hydrophilic moieties, coupled with the enhancement in surface polarity and free energy, collectively contributes to an improved adhesion between the metal film and the PMMA substrate. The essential reason that the adhesion strength between Au film and PMMA increase after UV lamp illuminating PMMA substrate can be understood as in the following: the photolysis of ester groups and the photo oxidation of methyl and methylene groups caused by the UV/ozone modification result in the generation of some polar oxygen-containing functional groups, including alcohols, carboxylic acids, ketones and aldehydes. It is the presence of these polar oxygen-containing functional groups that increases the wettability of the modified PMMA surface. These oxygen-containing polar functional groups at the polymer surface interact strongly with the deposited metal atoms/ions, and some strong chemical bonds between the polymer surface and the metal film are established, which is beneficial for the adhesion enhancement [10].

The aforementioned experiments analyzed the physical and chemical changes on the PMMA surface induced by UV/ozone modification, including surface morphology, water contact angle, and infrared absorption spectra. However, there was no direct manifestation of the enhanced film-substrate adhesion that we sought. To verify whether the adhesion between the PMMA samples treated with UV/ozone modification and metal films is indeed strengthened, we deposited Au films on the modified and unmodified PMMA surfaces using magnetron sputtering, followed by adhesive strength testing using the 3 M tape method. The 3 M tape, manufactured by the company 3 M, is chosen for its strong adhesive strength, stable viscosity, and non-residue properties. These advantages have made it a common choice among researchers globally for measuring the adhesion strength between metal films and polymer substrates. The tape adhesion strength testing method requires the division of the film into a grid pattern. Therefore, we utilized a contact mask template with a hole diameter of 1 mm and a spacing of 1 mm to deposit Au discs on the surfaces of both unmodified PMMA and 30-min UV illuminated PMMA. Subsequently, a strip of 3 M tape was adhered to the surface of each sample by applying pressure, ensuring complete adhesion between the tape and the PMMA substrate, as seen in Figure S1. Finally, the tape was quickly pulled with force. The results of the adhesion strength testing are shown in Fig. 5. The 3 M Scotch tape pull test reveals that very few Au discs deposited on UV/ozone modified PMMA are detached (see Fig. 5b and d), in high contrast to the case of Au discs deposited on unmodified PMMA for which most Au discs are removed (see Fig. 5a and c). The fraction of Au remaining changed from 10% for Au deposited on unmodified PMMA to 95% on 30 min UV light illuminated PMMA. The fraction of Au remaining is not lower than literature reported 85–95% Au remaining on UV/ozone chamber treated PMMA [10], higher than ~ 35% aluminum remaining on oxygen-rich plasma treated PMMA [23], ~ 30% Au remaining on plasma treated PMMA. ~ 50% Au remaining on toluene treated PMMA and ~ 90% Au remaining on chloroform treated PMMA [24]. The enhanced adhesion between the Au discs and substrate after our UV illumination treatment indicates a noticeable improvement in the binding strength between a metal film and a polymer substrate.

Fig. 5
figure 5

Images of Au discs on a unmodified and b modified PMMA surfaces before the 3 M tape adhesive strength testing, and after the removal of 3 M tape from the surfaces of Au discs on (a) unmodified and (b) modified PMMA. The areas enclosed by the blue lines indicate the regions where the 3 M tape adhered to the surface

Full size image

Upon successfully addressing the Au adhesion issue on PMMA, we proceeded to deposit continuous Au films on PMMA substrates exposed to 30 min of UV illumination. Utilizing a 40 W magnetron sputtering process, Au films were meticulously deposited at a calibrated rate of 0.45 nm/s. In order to achieve Au films that maintain transparency in the visible light spectrum, exceedingly thin Au layers were applied. The resultant deposition times, film thicknesses, and average transmittances across the visible light range are detailed in Table 2. The UV–visible spectroscopy measurements of sample transmittance within the visible light spectrum are presented in Fig. 6. Notably, the intrinsic optical transmittance of a PMMA substrate extends to approximately 92% across the entire visible light range, rendering it suitable for optical applications. Subsequent to the Au film deposition, the transmittance of Au/PMMA configurations gradually diminishes with increasing film thickness.

Table 2 Relationship among Au deposition time, deposited Au film thickness, and average transmittance for Au/PMMA with various Au thicknesses
Full size table
Fig. 6
figure 6

Relationship curve between the thickness of deposited Au film on PMMA surface and transmittance in visible light range

Full size image

The zenith of transmittance is observed at a wavelength of around 550 nm, lending a greenish hue to the light transmitted through an Au/PMMA window. Specifically, transmittances of 73%, 68%, and 62% are realized for Au film coatings of 7 nm, 11 nm, and 15 nm, respectively. These transmittance levels are well within acceptable limits for visualization purposes. However, when the Au film thickness is 27 nm, transmittance drops significantly to 41%. This reduction renders the configuration unsuitable for optical windows and aircraft canopies. These outcomes underscore the critical threshold of a continuous Au film thickness, which should ideally remain at or below 15 nm for effective utilization as optical glass within Au/PMMA systems.

Turning to Fig. 7, the electromagnetic interference (EMI) shielding efficiencies or attenutions of the Au/PMMA glass are showcased across a wide frequency spectrum encompassing S, C, X, and Ku bands. EMI shielding efficiency or attenution serves as a key indicator of EMI shielding effectiveness, where higher absolute values signify enhanced shielding prowess. the EMI shielding efficiency for vertical wave illumination was measured using the microwave network analyzer, which quantifies the impedance mismatch between two RF components, maximizing power efficiency and signal integrity. When an RF signal is transmitted from one component to another, part of the signal will be reflected, another part will be absorbed, and the rest will pass through the component. Figure 7a shows the testing diagram of the electromagnetic shielding efficiency of the microwave network analyzer. The microwave network analyzer uses S parameter as the evaluation standard of EMI shielding efficiency, where S11 is defined as the proportion of reflected signal energy at port 1 to the input signal energy, and S21 is defined as the proportion of signal energy transmitted to port 2 through the device under test to the input signal energy at port 1. In electromagnetic shielding test, S21 is commonly used to evaluate the efficiency of electromagnetic shielding.

Fig. 7
figure 7

a The testing diagram of the electromagnetic shielding efficiency. b Relationship Between Film Thickness and Electromagnetic Shielding Efficiency for different frequencies of waves covering S (2–4 GHz), C (4–8 GHz), X (8–12 GHz), and Ku (12–18 GHz) bands

Full size image

The trends depicted in Fig. 7b reveal that electromagnetic shielding efficiency escalates with augmented Au film thickness. This is because when the electromagnetic wave passes through the conductive film, the electromagnetic wave energy is partially attenuated by the influence of ohmic loss. With the increase of the thickness of the conductive layer, the sheet resistance (\({R}_{s}\)) decreases gradually, resulting in the increase of ohmic loss. Bright et al. [25] obtained the corresponding detailed mathematical expression by using the relationship between sheet resistance and electromagnetic shielding efficiency:

$${\text{SE}}=-20\times {{\text{log}}}_{10}\left(\frac{1+{\varepsilon }_{r}}{2\sqrt{{\varepsilon }_{r}}}+\frac{{\eta }_{0}}{2\sqrt{{\varepsilon }_{r}}{R}_{s}}\right)$$
(1)

Where \({\eta }_{0}\) is the free-space impedance, which is a constant. And \({\varepsilon }_{r}\) is the dielectric constant of the substrate, which is also a constant.

In the expression (1),

$${R}_{s}=\frac{{\rho }_{f}}{d}$$
(2)

where \({\rho }_{f}\) is the resistivity of the Au film, and \(d\) is the thickness of the Au film. Therefore, as the thickness of the Au film increases, the \({R}_{s}\) gradually decreases, and the electromagnetic shielding efficiency will be higher.

Evidently, Au films with thicknesses of 7 nm, 11 nm, and 15 nm all prove viable for transparent EMI shielding applications. Notably, attenuations of Au/PMMA samples with thicknesses of 7 nm, 11 nm, and 15 nm range from 17–15 dB, 23.5–17.5 dB, to 26–21 dB across the wavelength interval of 2.6–12.0 GHz. Depending on the specific requirements of visible light transmittance and EMI shielding efficiency, the choice of Au/PMMA glass with an appropriate Au film thickness remains a flexible option.

3 Conclusion

This study introduced and systematically investigated the surface modification of PMMA through the utilization of a 36W low-pressure mercury vapor lamp in open space. Furthermore, the deposition and characteristics of ultrathin, transparent Au films on PMMA were thoroughly examined. The obtained results underscored the efficacy of low-power lamp illumination for PMMA surface modification, achievable within a span of 20–30 min in open space. Importantly, this innovative approach demonstrates scalability, enabling its application for extensive surface treatments through the addition of multiple lamps. Remarkably, Au films with thicknesses as modest as 11–15 nm exhibited remarkable visibility and robust electromagnetic interference shielding (EMI) efficiency across a broad spectrum of wavelengths ranging from 2 to 12 GHz. This dual functionality highlights the potential of such films for both optical clarity and effective EMI mitigation. This research thus presents a versatile solution for enhancing PMMA surface properties and enabling its application in various domains, from optical components to EMI-sensitive environments.