Micro and Nanostructures

Tuning Optical Properties of Diamond-Like Carbon Films via Post-thermal Treatment

--Manuscript Draft--

Manuscript Number: MICRNA-D-25-00597

Article Type: Research Paper

Keywords: Sputtering; DLC; annealing; bandgap; extinction; Urbach

Abstract: In recent years, many optical industries have shown interest in employing diamond-like
carbon (DLC) coatings in their products. DLC layers were successfully deposited using
a low frequency pulsed magnetron sputtering system on glass substrates at room
temperature. Post-thermal treatments were performed on the coated substrates at
various temperatures of 150C, 200C and 250C. Raman spectroscopy and X-ray
photoelectron spectroscopy (XPS) revealed significant structural changes in the DLC
layers as a result of the thermal post-treatment process. Additionally, the morphology
of the layers was analyzed using field emission scanning electron microscopy
(FESEM). Furthermore, UV-visible spectroscopy was utilized to investigate the optical
properties of the films. The optical parameters of the deposited DLC layers were
subsequently calculated. The results demonstrated that the optical properties of the
coated DLC films could be effectively tuned through post-thermal treatment at relatively
low temperatures.

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Highlights

 Pulsed sputtered DLC films were tuned via Cost-Effective low-temperature annealing.
 DLC films revealed a significant morphological transformation under post treatment.
 Transition of sp² cluster toward nanocrystalline graphite structures confirmed.
 Induced chemical groups modifies optical conductivity and dielectric properties.
 Optical bandgap reduction enabling precise control over the films' optical behavior.
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Manuscript File Click here to view linked References

Tuning Optical Properties of Diamond-Like Carbon Films via Post-

thermal Treatment
M. Eshghabadi*, R. Safari, F. Sohbatzadeh, M. H. Mohammed

Atomic and Molecular Physics Department, Faculty of Basic Sciences, University of Mazandaran,
Babolsar, Iran
Email: eshghabadi@gmail.com
Keywords: Sputtering, DLC, annealing, graphite, bandgap, extinction, Urbach.

Abstract
In recent years, many optical industries have shown interest in employing diamond-like carbon
(DLC) coatings in their products. DLC layers were successfully deposited using a low
frequency pulsed magnetron sputtering system on glass substrates at room temperature. Post-
thermal treatments were performed on the coated substrates at various temperatures of 150C,
200C and 250C. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) revealed
significant structural changes in the DLC layers as a result of the thermal post-treatment
process. Additionally, the morphology of the layers was analyzed using field emission scanning
electron microscopy (FESEM). Furthermore, UV-visible spectroscopy was utilized to
investigate the optical properties of the films. The optical parameters of the deposited DLC
layers were subsequently calculated. The results demonstrated that the optical properties of the
coated DLC films could be effectively tuned through post-thermal treatment at relatively low
temperatures.
Introduction
Diamond-like carbon (DLC), due to its unique physical properties, has a wide range of
applications spanning industrial and medical fields. These diverse applications stem from the
composition of sp³ and sp² carbon hybridizations, which can be tuned by selecting appropriate
deposition methods. For instance, in one study, a chemical vapor deposition (CVD) system
with hydrocarbon gas serving as the carbon precursor was employed to prepare a DLC layer
on a silicon (Si) substrate for investigating its water-repellent and magnetic properties [1].
However, these days, plasma environments are commonly used for preparing DLC layers,
owing to the presence of ionized species such as reactive radicals. Atmospheric pressure
plasma-enhanced chemical vapor deposition (AP-PECVD) is a popular technique because it
requires less expensive equipment. In several studies, atmospheric pressure plasma systems
were used to prepare DLC layers with enhanced erosion resistance and higher hardness [2-5].
However, vacuum-based plasma coating systems offer advantages, such as a clean atmosphere
and better control over parameters. Plasma-enhanced chemical vapor deposition (PECVD) is
regularly employed for DLC layer deposition. For example, in two studies, RF-PECVD was
used with different flow gas to deposit DLC layers using CH₄ gas as a hydrocarbon precursor
[6, 7]. In another study, DLC thin film with unique surface morphology was coated using the
plasma immersion technique [8]. Cathodic arc deposition is another effective method for
producing DLC layers with specific corrosion resistance properties [9]. Additionally, reactive
sputtering is a common technique for depositing Nitrogen dopped DLC with tailored wetting
and structural properties [10]. In some works, non-reactive sputtering system using high purity
graphite target and tunning the substrate temperature employed for preparing DLC films [11-
13].
Besides of all outstanding properties, the optical properties of DLC films, such as refractive
index, absorption, and bandgap, are critical for many optical and photonic applications,
including protective coatings, sensors, and optoelectronic devices. The optical characteristics
of DLC are highly dependent on the ratio of sp² to sp³ hybridized carbon atoms, which can be
modulated through the deposition process and post-deposition treatments. Several studies have
explored these properties, showing that DLC films typically exhibit high optical transparency
in the visible region, combined with excellent hardness and low friction. For instance, Tshomo
et al. [14] investigated the optical properties of DLC films deposited by DC-PECVD,
highlighting the influence of the sp²/sp³ ratio on the bandgap and refractive index. However,
Lu et al changes the optical properties not by changing temperature of the substrates but by
doping Oxygen in to the DLC structure using pulsed laser deposition (PLD) system in Oxygen
ambient [15]. They successfully deposited anti reflective DLC film. Mbiombi et al, also tunned
optical properties of DLC film by applying bayas voltage using PLD too [16]. RF-Magnetron
sputtering system employed by Majeed et al to deposit metal-doped DLC optical films [17].
They tuned optical properties of the films via tuning percentage of concentration metallic
dopant. Choosing a low cost yet efficient method for tunning of DLC optical properties is very
crucial for successfully approaching applicable industrial techniques.
In this study, the optical properties of thermal post-treated DLC layers prepared using
magnetron sputtering have also been investigated. Optical and electrical parameters of the
treated layers successfully tuned in terms of post-treatment conditions. The results showed that,
the objective of developing a straightforward, cost-effective but reliable technique was
successfully accomplished.
Experimental Section
Sixteen soda-lime glass substrates, each measuring 2cm × 1cm, were prepared by ultrasonic
cleaning in high-purity acetone, ethanol, and double-distilled water for 10 minutes respectively.
The substrates were subsequently dried using clean, heated air to ensure surface cleanliness
prior to deposition.

Fig. 1. Low frequency pulsed planar magnetron sputtering system

A low frequency (50 Hz) pulsed planar magnetron sputtering system equipped with a graphite
target was employed to deposit diamond-like carbon (DLC) films onto glass substrates.
Schematic of deposition system can be seen in figure 1. Deposition was carried out at a power
of 120W and a frequency of 50 Hz for 15 minutes. A high-purity graphite target (carbon source)
and 99.999% pure argon gas were used.
Following the deposition process, the samples were annealed at 150°C, 200°C, and 250°C,
while the control sample remained unannealed.
Morphology analysis
Field Emission Scanning Electron Microscopy (FESEM) was used to obtain images of the
thermally post-treated DLC films deposited on glass substrates.

Fig. 2. FESEM images of the layers post-thermal treated at various temperatures

The FESEM images in figure 2 clearly demonstrate significant structural changes in the treated
layers. In all images, the layer fully covers the substrate. Additionally, independent structures
are observed on the uniform underlying layer.
In the control sample, formless, particle-like structures are randomly dispersed across the fine,
uniform context. These particle-like structures vary widely in size and shape, ranging from
very fine particles to much larger, irregular fragments. In the sample treated at 150°C, the
formless particle-like structures disappear, while small, seed-like structures begin to emerge
on a cauliflower-shaped patterned context. The average diameters of these seed-like structures
in samples treated at 150°C, 200°C, and 250°C are approximately 52nm, 88nm, and 155nm,
respectively.
The size of the seeds increases significantly with higher treatment temperatures, while the
underlying structure transitions from coarser textures to finer, higher-contrast features with
shallow cracks. The presence of scattered high-contrast dots on the underlying layer suggests
the formation of sharp-headed, rough structures or secondary electron-dense features.
The structural changes observed in the post-treated samples indicate that the irregular, particle-
like structures in the untreated sample disassemble into finer structures at 150°C. The
morphology of the underlying layer evolves into coarser, sharp-headed features, while the seed-
like structures grow significantly, tripling in size in the sample treated at 250°C.
Raman Analysis of DLC Films
Raman shifts spectroscopy serves as a robust method employed to study the nature of carbon
bonds in diamond-like carbon (DLC) layers. This Approach relies on the assessment of sp² and
sp³ hybridized carbon atoms. The Raman spectrum of a DLC film typically exhibits two
prominent peaks: the D peak and the G peak.
The D band, referred to as the disorder band, is attributed to the breathing modes of sp² sites in
aromatic rings, whereas the G band, known as the graphitized band, corresponds to the
stretching vibrational modes of sp² sites in both chains and aromatic rings [18-21].
The relative intensities of the D and G peaks (ID/IG), the full width at half maximum (FWHM)
of the G peak, and the G peak position are crucial parameters for determining the sp³-to-sp²
content ratio, size of sp² cluster, and nature of structural modification in DLC deposited layers.
The ID/IG ratio is directly related to the sp²/sp³ bonding fraction. An elevated ID/IG proportion
signifies a greater presence of sp²/sp³ sites within planar ring structures or clustering structures.
The FWHM of the G peak serves as a qualitative indicator of sp² clustering, with a broader
FWHM generally correlating to a lower sp² clustered content. The G peak position provides
valuable insights into the type of structural transitions occurring in the DLC film. A shift in the
G peak position towards higher wavenumbers indicates a transition from an amorphous state
to a graphitized state and nano crystalline graphite structures [22-26].
Figure 3 presents the Raman spectra of DLC deposited layers annealed at various temperatures.
 Fig. 3. Raman spectra of deposited layers annealed in different temperature:
a) Control, b)150, c)200, d)250
By deconvoluting the Raman shift patterns, analyzed through Gaussian curve fitting, reveal
three separate peaks were observed at approximately 1100, 1370, and 1590 cm⁻¹. These peaks
are associated with disordered sp³ carbon, the D peak, and the G peak, respectively. The Raman
peak at 1100 cm⁻¹ might be attributed to C–H in the aromatic rings [24, 27]. As illustrated in
figure 4, annealing the DLC films resulted in an increase in the ID/IG ratio, a decrease in the
full width at half maximum (FWHM) of the G peak, and a shift of the G peak position to higher
wavenumbers. The increase in the ID/IG ratio suggests a preference for sp² sites in aromatic ring
structures over chain structures or formation of nano crystalline graphite structures. In addition,
an increase in the intensity of D peak refers to formation of structural defects or introduction
of functional groups, disrupting the sp² carbon lattice [27]. A decrement in the full width at half
maximum (FWHM) of the G peak indicates an increment in sp² sites contribution.

Furthermore, the shift in G peak position Indicates a transformation in structure, transitioning

from an amorphous state to a graphitized form [23, 24, 26].
The relationship between the ID/IG ratio and the average spatial size of the sp2 hybridized
regions can be explained by the following equation [24, 26]:

𝐼𝐷 1
𝐿𝑎 = √ ×
𝐼𝐺 𝐶𝜆

The wavelength of excitation is 532 nm and Cλ=0.55 nm− 2 is a scaling coefficient. It is clear,
by increment of the annealing temperature, the average spatial size of the sp² hybridized sites
increased reflecting the deposited coating's graphitization tendency represented in figure 4
[23]. The increasing intensity of the D peak, accompanied by a growing average spatial size of
the sp² hybridized regions, suggests the formation of structural defects or C=O groups within
these nanocrystalline graphitic sites.

Fig. 4. The ID/IG proportion besides La, location and the full width at half maximum
(FWHM) of the G peak versus the annealing temperatures.
.
XPS Analysis
XPS spectra were employed to analyze the chemical composition of the coated layers. By
deconvolution and Shirley background subtraction of the C1s spectra of the samples, three
peaks were identified. The C1 peak at 284.6 eV associated with graphitized structures [22, 24].
XPS Spectra of the layers can be seen in figure 5. The C3 peak at 285 eV corresponds to C–C
or C–H compounds and the C2 peak at 288.5 eV corresponds to C=O compounds [28]. The
existence of sp2 and sp3 hybridizations, along with oxidized carbon, is fully supported by
Raman spectra. The decreasing intensity of the C1 peak, associated with graphitic carbon, and
the increasing intensity of the C3 peak, associated with C=O compounds, indicate that the
contribution of graphitic structures to sp2 hybridization partially has been replaced by C=O
compounds.

Fig. 5. XPS spectra of deposited layers annealed in different temperatures:

a)150C, b)200C, c)250C
Optical and Electrical Characteristics of DLC layers
The optical and electrical characteristics of temperature-treated DLC layers were analyzed by
measuring their absorption (A), transmittance (T), and reflectance (R) spectra. These
measurements were conducted across the wavelengths from infrared to ultraviolet region. As
illustrated in figure 6, annealing DLC films from 150°C to 250°C resulted in increased optical
absorption and reflectance, accompanied by a corresponding decrease in optical transmittance.
This behavior is attributed to the reduction of hydrogen content and C–H sp³ carbon bonds,
which facilitates an increment in sp² hybridized carbon atoms within aromatic rings [29-34].

Fig. 6. The effect of annealing temperature on optical spectra of the deposited DLC layers
The absorption coefficient (α) can be calculated using the equation provided below [35, 36]:
1 1 − R2
α = Ln( )
t T
where R and T denote the optical reflectance and transmittance intensities, respectively, while
t denotes the thickness of the deposited films. Figure 7 illustrates the variation of the absorption
coefficient with both wavelength and photon energy. As indicated by the results, annealing
DLC films at 250°C leads to a reduction in the absorption coefficient within both the visible
and ultraviolet ranges. This observation aligns with the findings presented in figure 6.

Fig. 7. The effect of annealing temperature on the absorption coefficient of deposited DLC
layers.
Figure 8 illustrates the variation in the bandgap of the deposited DLC films with annealing
temperatures up to 250°C. In semiconductors, electrons can absorb photons carrying energies
greater than the bandgap energy enable electron transitions from the valence band to the band
of conduction. Eg referring to the optical bandgap was calculated using the α called absorption
coefficient based on the Tauc relationship [35, 36]:

(αhν)1/n = A(hν − Eg )

In this equation, (αhν)1/n represents the Tauc relation, where α, hν, denote the coefficient of
absorption, energy of photon, respectively and A is a constant. The parameter n referring to a
constant equal to 0.5 in case of direct bandgap and 2 in case of indirect bandgap transitions.
The findings indicate that the electronic transition in DLC layers is an indirect transition.
Additionally, the optical bandgap of DLC layers is inversely proportional to the size and
concentration of sp² in graphite clusters. A reduction in the bandgap corresponds to a π-π*
transition associated with the sp² structure [35-38]. It can be seen in figure 8, the bandgap of
the DLC deposited layers reduced from 1.66 eV to 1.25 eV with increasing annealing
temperature, due to the growth in the number of sp² sites and the size of sp² clusters.
 Fig. 8. Bandgap of annealed DLC layers at different temperatures.
A critical parameter for characterizing inhomogeneous disorder arising from varying sp2 cluster
sizes is the Urbach energy [39, 40]. In the case of amorphous carbon layers, the Urbach energy
is defined via the following equation [36]:
hυ
Ln(α) = Ln(α0 ) −
Eu
In the Urbach energy equation, α represents the absorption coefficient, α₀ is a constant, hʋ
denotes the incident photon energy, and Eu represents the Urbach energy. The Urbach energy
can be determined by calculation of the slope in the ln(α)-hʋ plot. As depicted in figure 9,
annealing DLC films in range from 150°C to 250°C results in an increase in Urbach energy
from 1.22 eV to 1.92 eV.
 Fig. 9. Urbach energy of annealed DLC layers at different temperatures.
The extinction coefficient was analyzed to quantify the attenuation of electromagnetic waves
within the medium, as described by the following equation [39]:
𝛼𝜆
𝑘=
4𝜋
As shown in figure 10, the extinction coefficient of the DLC films increases with annealing
temperature, which is consistent with the behavior of the absorption coefficient.
 Fig. 10. Variation of the extinction coefficient of annealed DLC layers in different
temperatures versus wavelength.
Figure 11 indicates variation of refractive index of the DLC films at different annealing
temperatures according the following equation [3]:
4𝑅 2 1/2
𝑅+1
𝑛 = [( ) − 𝑘 ] −
(1 − 𝑅)2 𝑅−1
In this equation reflectance coefficient denoted by R and the extinction coefficient represented
by k. As illustrated, annealing the films at 250°C leads to an increase in the refractive index.
This increase can be attributed to two primary factors: 1) the growth of sp2 cluster size,
resulting in a change in light polarization [41], and 2) the enhanced dehydrogenation of carbon
structures [42].

Fig. 11. variation of refractive index of annealed DLC layers at different temperatures.
The dielectric constant indicates the ability of medium to store the energy [23] . Figure 12
shows the effect of annealing temperature on dielectric contestant of deposited films. The Real
component of the complex dielectric permittivity is responsible for propagation of energy while
the imaginary of it, indicate the absorption of electromagnetic energy. The complex dialectic
constant is [43] 𝜀 = 𝜀1 + 𝑖𝜀2 that 𝜀1 = 𝑛2 − 𝑘 2 and 𝜀2 = 2𝑛𝑘 where index of refractive
denoted by n and extinction constant represented by k.

Fig. 12. The complex dielectric constant of annealed DLC layers at various temperatures.
As illustrated, annealing the films at 250°C leads to an increase in the real component of the
dielectric permittivity, indicating an enhancement in material polarization due to increased
lattice disorder. The dielectric constant can be influenced by disorder within the π electron
states. Given the relatively weak binding of π electrons, their energy levels are nearer to the
Fermi level than the σ states. Consequently, the valence band mainly consists of fully occupied
π states, while the conduction band is primarily made up of unoccupied π* states. Irregularities
in the π states impede carrier mobility, enhancing the dielectric characteristics of these films
[44]. The imaginary component of the complex permittivity corresponds to the absorption of
electromagnetic energy during transitions from valence states to conduction states. In line with
the annealing temperature of 250°C, the absorbed energy content increases. These findings are
consistent with the bandgap results presented in figure 9. As the annealing temperature rises
from 150°C to 200°C, the bandgap decreases significantly from 1.57 eV to 1.29 eV, suggesting
an increase in absorbed energy, as depicted in figure 10.
The tanδ referring to dissipation factor, quantifies the rate of energy dissipation in a lossy
environment. Electrical potential energy is lost as dissipation in the form of heat in all
insulating substances. The dissipation factor is determined with the aid of equation provided
bellow [43]:
𝜀2
tan(𝛿) =
𝜀1
According to obtained results in figure 13, with increasing the annealing temperature to 250°C,
the rate of increasing the absorbed energy is more than its propagation, especially, from 200°C
to 250°C.
 Fig. 13. The dissipation factor of the annealed DLC layers at various temperatures.
Optical conductivity serves as an indicator of electron transitions to the conduction band, which
demand an adequate energy supply. This energy is delivered by photons with sufficiently high
energy, enabling electrons bound to atoms to make the transition. The effect of increasing
annealing temperatures on the optical conductivity is shown in figure14 following equation
[23]:
𝜎 = 𝜎1 + 𝜎2
𝜎1 = 𝜔𝜀2 𝜀0 ∝ 𝑛𝑐𝛼
𝑐
𝜎2 = 𝜔𝜀1 𝜀0 ∝ (𝑛2 − 𝑘 2 )
𝜆
In these relations, the frequency of the incident light is represented by ω, C stands for the
velocity of light, n denotes the refractive index, α symbolizes the absorption coefficient, and
the extinction coefficient is denoted by k. The variation patterns of σ1 and σ2 exhibit similarities
to the respective patterns of to ε2 and ε1.
 Fig. 14. The optical conductivity of annealed DLC layers at various temperatures.
Conclusion
In summary, DLC layers with tunned optical and electrical properties successfully deposited
on the glass substrates. The structural, optical, and electrical evolution of diamond-like carbon
(DLC) films deposited on glass substrates under varying annealing temperatures. The results
indicate that annealing significantly influences the morphology and composition of DLC films,
promoting the transition from an amorphous to a graphitized phase. Raman spectroscopy
reveals that increasing the annealing temperature enhances the sp² cluster size and content,
accompanied by a shift in the G peak position and an increase in the ID/IG ratio, reflecting the
formation of nanocrystalline graphite structures.
Morphological analysis using FESEM shows distinct temperature-dependent structural
transformations, with seed-like nanostructures forming and growing at higher annealing
temperatures. The optical and electrical properties of the films were systematically altered, with
increased absorption, reflectance, refractive index, and dielectric constants observed at 250°C.
These changes correlate with a reduction in the bandgap and the growth of sp² clusters, as
confirmed by Tauc plot analysis and Urbach energy trends.
The XPS analysis corroborates these findings by identifying variations in carbon hybridization
and the emergence of oxygen-containing functional groups. The study further demonstrates
that annealing enhances the films’ optical conductivity and energy dissipation, while modifying
their dielectric response, indicative of increased lattice polarization and carrier transport
constraints.
Therefore, annealing emerges as a critical parameter for tailoring the structural and functional
properties of DLC films. These findings provide a foundation for optimizing DLC films for
advanced optical, electronic, and dielectric applications, particularly where controlled
graphitization and enhanced sp² content are desired.
Ref.s
1. Han, H., F. Ryan, and M. McClure, Ultra-thin tetrahedral amorphous carbon film as slider
overcoat for high areal density magnetic recording. Surface and Coatings Technology, 1999.
120: p. 579-584.
2. Ghadai, R.K., et al., Structural and mechanical analysis of APCVD deposited diamond-like
carbon thin films. Silicon, 2021. 13(12): p. 4453-4462.
3. Gharibyan, A., et al., Preparation of wide range refractive index diamond-like carbon films by
means of plasma-enhanced chemical vapor deposition. Applied optics, 2011. 50(31): p. G69-
G73.
4. Sohbatzadeh, F., et al., Development of a radio frequency atmospheric pressure plasma jet
for diamond-like carbon coatings on stainless steel substrates. Applied Physics A, 2016. 122:
p. 1-9.
5. Yu, S.-E., et al., Direct Current Pulse Atmospheric Pressure Plasma Jet Treatment on
Electrochemically Deposited NiFe/Carbon Paper and Its Potential Application in an Anion-
Exchange Membrane Water Electrolyzer. Langmuir, 2024. 40(29): p. 14978-14989.
6. Grischke, M., et al., Variation of the wettability of DLC-coatings by network modification
using silicon and oxygen. Diamond and Related Materials, 1998. 7(2-5): p. 454-458.
7. Grayeli, A., Structure and Optical Characteristics of DLC Films: A Study on the Impact of CH4
Flow Rate. Vakuum in Forschung und Praxis, 2023. 35(5): p. 34-38.
8. Sokół, J.M., et al., Diamond-like carbon conversion surfaces for space applications. Journal of
Applied Physics, 2024. 135(18).
9. Wu, S., et al., Relationship between residual stress and tribocorrosion behavior of high
quality DLC coatings prepared by FCVA with HVP technology. Ceramics International, 2024.
10. Jankauskas, Š., et al., Study of the structure, composition and wettability of the DLC: N films.
Surface and Coatings Technology, 2024. 489: p. 131132.
11. Afshar, A., et al., Effect of substrate temperature on structural properties and corrosion
resistance of carbon thin films used as bipolar plates in polymer electrolyte membrane fuel
cells. Journal of alloys and compounds, 2010. 502(2): p. 451-455.
12. Larijani, M., et al., A comparison of carbon coated and uncoated 316L stainless steel for using
as bipolar plates in PEMFCs. Journal of Alloys and Compounds, 2011. 509(27): p. 7400-7404.
13. Tan, X., et al., Microstructures and visible-infrared optical properties of diamond-like carbon
films deposited by magnetron sputtering. Diamond and Related Materials, 2023. 133: p.
109724.
14. Tshomo, S., et al., Optical properties of Diamond like Carbon films prepared by DC-PECVD.
Malaysian Journal of Fundamental and Applied Sciences, 2012. 8(2).
15. Lu, Y., et al., Pulsed laser deposition of the protective and Anti-reflective DLC film. Infrared
Physics & Technology, 2021. 119: p. 103949.
16. Mbiombi, W.M., et al., Tuning structural, electrical and mechanical properties of diamond-
like carbon films by substrate bias voltage. Materials Today Communications, 2021. 28: p.
102501.
17. Majeed, S., et al., RF magnetron sputtered deposited metal-doped diamond like carbon thin
films: structural, morphological, mechanical, and optical properties. Journal of Ovonic
Research, 2022. 18(3).
18. Robertson, J., Diamond-like carbon. Pure and applied chemistry, 1994. 66(9): p. 1789-1796.
19. Robertson, J., Plasma deposition of diamond-like carbon. Japanese Journal of Applied
Physics, 2011. 50(1S1): p. 01AF01.
20. Safari, R. and F. Sohbatzadeh, Effect of electrical discharge power on mechanical properties
of N-DLC films deposited by atmospheric DBD plasma. Superlattices and Microstructures,
2020. 145: p. 106633.
21. Sohbatzadeh, F., et al., Characterization and performance of coupled atmospheric pressure
argon plasma jet with n-hexane electrospray for hydrophobic layer coatings on cotton textile.
Diamond and Related Materials, 2019. 91: p. 34-45.
22. Robertson, J., Diamond-like amorphous carbon. Materials science and engineering: R:
Reports, 2002. 37(4-6): p. 129-281.
23. Safari, R., F. Sohbatzadeh, and T. Mohsenpour, Optical and electrical properties of N-DLC
films deposited by atmospheric pressure DBD plasma: Effect of deposition time. Surfaces and
Interfaces, 2020. 21: p. 100795.
24. Sohbatzadeh, F., M. Eshghabadi, and T. Mohsenpour, Controllable synthesizing DLC nano
structures as a super hydrophobic layer on cotton fabric using a low-cost ethanol
electrospray-assisted atmospheric plasma jet. Nanotechnology, 2018. 29(26): p. 265603.
25. Bagheri, H., et al., A novel combination of non-thermal plasma process and a heterogenous
nanophotocatalyst-sorbent comprising zinc sulfide, graphene oxide and polyaniline as an
efficient strategy for treatment of organic-contaminated water. Journal of Water Process
Engineering, 2023. 55: p. 104254.
26. Ferrari, A.C. and J. Robertson, Raman spectroscopy of amorphous, nanostructured,
diamond–like carbon, and nanodiamond. Philosophical Transactions of the Royal Society of
London. Series A: Mathematical, Physical and Engineering Sciences, 2004. 362(1824): p.
2477-2512.
27. Sun, Y., et al., The effects of hydroxide and epoxide functional groups on the mechanical
properties of graphene oxide and its failure mechanism by molecular dynamics simulations.
RSC advances, 2020. 10(49): p. 29610-29617.
28. Garriga, R., et al., Multifunctional, biocompatible and pH-responsive carbon nanotube-and
graphene oxide/tectomer hybrid composites and coatings. Nanoscale, 2017. 9(23): p. 7791-
7804.
29. Biswas, H.S., et al., Optimized study of the annealing effect on the electrical and structural
properties of HDLC thin-films. RSC advances, 2022. 12(46): p. 29805-29812.
30. Peng, J., et al., Solid state magnetic resonance investigation of the thermally-induced
structural evolution of silicon oxide-doped hydrogenated amorphous carbon. Carbon, 2016.
105: p. 163-175.
31. Dingemans, G., et al., Influence of annealing and Al2O3 properties on the hydrogen-induced
passivation of the Si/SiO2 interface. Journal of Applied Physics, 2012. 111(9).
32. Wu, Y., et al., Effect of vacuum annealing on the microstructure and tribological behavior of
hydrogenated amorphous carbon films prepared by magnetron sputtering. Proceedings of
the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2013.
227(7): p. 729-737.
33. Kumaravel, R., et al., Effect of annealing on the electrical, optical and structural properties of
cadmium stannate thin films prepared by spray pyrolysis technique. Thin Solid Films, 2010.
518(8): p. 2271-2274.
34. Hassanien, A.S. and A.A. Akl, Influence of composition on optical and dispersion parameters
of thermally evaporated non-crystalline Cd50S50− xSex thin films. Journal of Alloys and
Compounds, 2015. 648: p. 280-290.
35. Abadi, S.K.N., et al., Studying the effects of plasma produced species on the optical
characteristics and bonding structure of diamond-like carbon films deposited by direct
current unbalanced magnetron sputtering. Materials Chemistry and Physics, 2019. 229: p.
348-354.
36. Qi, M., et al., Effect of various nitrogen flow ratios on the optical properties of (Hf: N)-DLC
films prepared by reactive magnetron sputtering. Aip Advances, 2017. 7(8).
37. Jianrong, X., J. Aihua, and W. Zhiyong, Effect of nitrogen doping on the structure and optical
band gap of fluorinated diamond-like carbon films. Japanese Journal of Applied Physics,
2013. 52(9R): p. 095502.
38. Pandey, B., et al., Effect of nickel incorporation on microstructural and optical properties of
electrodeposited diamond like carbon (DLC) thin films. Applied surface science, 2012. 261: p.
789-799.
39. Carey, J. and S. Silva, Disorder, clustering, and localization effects in amorphous carbon.
Physical Review B—Condensed Matter and Materials Physics, 2004. 70(23): p. 235417.
40. Hansen, M., K. Anderko, and H. Salzberg, Constitution of binary alloys. Journal of the
Electrochemical Society, 1958. 105(12): p. 260C.
41. Sun, Y., X.-Y. Huang, and H. Wang, Influence of hydrogen content on optical and mechanical
performances of diamond-like carbon films on glass substrate. Journal of Materials
Engineering and Performance, 2016. 25: p. 1570-1577.
42. Sakr, G., et al., Optical spectroscopy, optical conductivity, dielectric properties and new
methods for determining the gap states of CuSe thin films. Journal of alloys and compounds,
2010. 507(2): p. 557-562.
43. Guerino, M., M. Massi, and R.D. Mansano, The influence of nitrogen and fluorine on the
dielectric constant of hydrogenated amorphous carbon (aC: H) films. Microelectronics
journal, 2007. 38(8-9): p. 915-918.
44. Fadel, M., et al., Structural and optical properties of SeGe and SeGeX (X= In, Sb and Bi)
amorphous films. Journal of Alloys and Compounds, 2009. 485(1-2): p. 604-609.
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Declaration of Interest Statement

Declaration of interests

☒The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests: