Editorial

Jump to: Research

2 pages, 151 KiB

Open AccessEditorial

Editorial for the Special Issue “Applications of Optical Thin Films”

by Jin-Cherng Hsu

Nanomaterials 2023, 13(8), 1387; https://0-doi-org.brum.beds.ac.uk/10.3390/nano13081387 - 17 Apr 2023

Viewed by 658

Abstract

Optical thin films have been vital to enhancing optical performance for many years [...] Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

Research

Jump to: Editorial

12 pages, 1530 KiB

Open AccessArticle

The Characteristics of the Metal-Free and Non-Conjugated Polymer Film with Self-Assembled Nanoparticles

by Kwang-Ming Lee, Chung-Cheng Chang, Jia-Ming Wang, Chia-Yu Chang and Chia-Hong Huang

Nanomaterials 2023, 13(3), 596; https://0-doi-org.brum.beds.ac.uk/10.3390/nano13030596 - 02 Feb 2023

Cited by 1 | Viewed by 1116

Abstract

It is shown in this paper that a polymer, MA-PEG 1000-DGEBA (MP1D), exhibits antireflection, substrate-dependent photoluminescence (SDP), wide band-gap, and photoconduction characterization. MP1D was synthesized from maleic anhydride, polyethylene glycol 1000, and bisphenol-A diglycidyl ether. Self-assembled nanoparticles embedded in MP1D film and ranging [...] Read more.

It is shown in this paper that a polymer, MA-PEG 1000-DGEBA (MP1D), exhibits antireflection, substrate-dependent photoluminescence (SDP), wide band-gap, and photoconduction characterization. MP1D was synthesized from maleic anhydride, polyethylene glycol 1000, and bisphenol-A diglycidyl ether. Self-assembled nanoparticles embedded in MP1D film and ranging from 2.5 to 31.6 nm are observed, which could be expected as scatterers to enhance light trapping and extraction. The size of the nanoparticle increases with the concentration of the MP1D solution. Besides solution concentration, the nanoparticle dimension could be modified by the chain length of polyethylene glycol in the polymer synthesis. The effects of solution concentration, annealing temperature, annealing period, and substrate on the photoluminescence (PL) of MP1D films are examined. Increasing solution concentration increases PL intensity. However, aggregation-caused quenching is explicit as the solution concentration exceeds 100 mM. PL intensity increases with annealing temperature, which could be attributed to crystallinity improvement. PL intensity increases with increasing the annealing period from 0.5 to 2 h. Nonetheless, as the annealing period exceeds 2 h, PL quenching is emerging, which could be due to aggregation. It is expected that MP1D could be a promising candidate for host materials and MP1D film could play a multifunctional role (antireflective and light-trapping functions) in optoelectronics. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Figure 1

15 pages, 3740 KiB

Open AccessEditor’s ChoiceArticle

Nanostructured PbS-Doped Inorganic Film Synthesized by Sol-Gel Route

by Adrian Ionut Nicoara, Mihai Eftimie, Mihail Elisa, Ileana Cristina Vasiliu, Cristina Bartha, Monica Enculescu, Mihaela Filipescu, César Elosúa Aguado, Diego Lopez, Bogdan Alexandru Sava and Mihai Oane

Nanomaterials 2022, 12(17), 3006; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12173006 - 30 Aug 2022

Cited by 4 | Viewed by 1850

Abstract

IV-VI semiconductor quantum dots embedded into an inorganic matrix represent nanostructured composite materials with potential application in temperature sensor systems. This study explores the optical, structural, and morphological properties of a novel PbS quantum dots (QDs)-doped inorganic thin film belonging to the Al [...] Read more.

IV-VI semiconductor quantum dots embedded into an inorganic matrix represent nanostructured composite materials with potential application in temperature sensor systems. This study explores the optical, structural, and morphological properties of a novel PbS quantum dots (QDs)-doped inorganic thin film belonging to the Al₂O₃-SiO₂-P₂O₅ system. The film was synthesized by the sol-gel method, spin coating technique, starting from a precursor solution deposited on a glass substrate in a multilayer process, followed by drying of each deposited layer. Crystalline PbS QDs embedded in the inorganic vitreous host matrix formed a nanocomposite material. Specific investigations such as X-ray diffraction (XRD), optical absorbance in the ultraviolet (UV)-visible (Vis)-near infrared (NIR) domain, NIR luminescence, Raman spectroscopy, scanning electron microscopy–energy dispersive X-ray (SEM-EDX), and atomic force microscopy (AFM) were used to obtain a comprehensive characterization of the deposited film. The dimensions of the PbS nanocrystallite phase were corroborated by XRD, SEM-EDX, and AFM results. The luminescence band from 1400 nm follows the luminescence peak of the precursor solution and that of the dopant solution. The emission of the PbS-doped film in the NIR domain is a premise for potential application in temperature sensing systems. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Graphical abstract

17 pages, 5228 KiB

Open AccessArticle

High Sensitivity SERS Substrate of a Few Nanometers Single-Layer Silver Thickness Fabricated by DC Magnetron Sputtering Technology

by Hsing-Yu Wu, Hung-Chun Lin, Guan-Yi Hung, Chi-Shun Tu, Ting-Yu Liu, Chung-Hung Hong, Guoyu Yu and Jin-Cherng Hsu

Nanomaterials 2022, 12(16), 2742; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12162742 - 10 Aug 2022

Cited by 6 | Viewed by 2234

Abstract

Surface-enhanced Raman spectroscopy (SERS) is commonly used for super-selective analysis through nanostructured silver layers in the environment, food quality, biomedicine, and materials science. To fabricate a high-sensitivity but a more accessible device of SERS, DC magnetron sputtering technology was used to realize high [...] Read more.

Surface-enhanced Raman spectroscopy (SERS) is commonly used for super-selective analysis through nanostructured silver layers in the environment, food quality, biomedicine, and materials science. To fabricate a high-sensitivity but a more accessible device of SERS, DC magnetron sputtering technology was used to realize high sensitivity, low cost, a stable deposition rate, and rapid mass production. This study investigated various thicknesses of a silver film ranging from 3.0 to 12.1 nm by field emission scanning electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. In the rhodamine 6G (R6G) testing irradiated by a He-Ne laser beam, the analytical enhancement factor (AEF) of 9.35 × 10⁸, the limit of detection (LOD) of 10⁻⁸ M, and the relative standard deviation (RSD) of 1.61% were better than the other SERS substrates fabricated by the same DC sputtering process because the results showed that the 6 nm thickness silver layer had the highest sensitivity, stability, and lifetime. The paraquat and acetylcholine analytes were further investigated and high sensitivity was also achievable. The proposed SERS samples were evaluated and stored in a low humidity environment for up to forty weeks, and no spectrum attenuation could be detected. Soon, the proposed technology to fabricate high sensitivity, repeatability, and robust SERS substrate will be an optimized process technology in multiple applications. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Figure 1

19 pages, 9166 KiB

Open AccessArticle

Orientation-Mediated Luminescence Enhancement and Spin-Orbit Coupling in ZnO Single Crystals

by Ali Hassan, Abbas Ahmad Khan, Yeong Hwan Ahn, Muhammad Azam, Muhammad Zubair, Wei Xue and Yu Cao

Nanomaterials 2022, 12(13), 2192; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12132192 - 26 Jun 2022

Cited by 3 | Viewed by 1455

Abstract

Temperature-, excitation wavelength-, and excitation power-dependent photoluminescence (PL) spectroscopy have been utilized to investigate the orientation-modulated near band edge emission (NBE) and deep level emission (DLE) of ZnO single crystals (SCs). The near-band-edge emission of ZnO SC with <0001> orientation exhibits strong and [...] Read more.

Temperature-, excitation wavelength-, and excitation power-dependent photoluminescence (PL) spectroscopy have been utilized to investigate the orientation-modulated near band edge emission (NBE) and deep level emission (DLE) of ZnO single crystals (SCs). The near-band-edge emission of ZnO SC with <0001> orientation exhibits strong and sharp emission intensity with suppressed deep level defects (mostly caused by oxygen vacancies V_o). Furthermore, Raman analysis reveals that <0001> orientation has dominant E₂ (high) and E₂ (low) modes, indicating that this direction has better crystallinity. At low temperature, the neutral donor-to-bound exciton (D^oX) transition dominates, regardless of the orientation, according to the temperature-dependent PL spectra. Moreover, free-exciton (FX) transition emerges at higher temperatures in all orientations. The PL intensity dependence on the excitation power has been described in terms of power-law (I~L^α). Our results demonstrate that the α for <0001>, <1120>, and <1010> is (1.148), (1.180), and (1.184) respectively. In short, the comprehensive PL analysis suggests that D^oX transitions are dominant in the NBE region, whereas oxygen vacancies (V_o) are the dominant deep levels in ZnO. In addition, the <0001> orientation contains fewer V_o-related defects with intense excitonic emission in the near band edge region than other counterparts, even at high temperature (~543 K). These results indicate that <0001> growth direction is favorable for fabricating ZnO-based highly efficient optoelectronic devices. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Graphical abstract

11 pages, 5736 KiB

Open AccessArticle

Design of a High-Efficiency Multilayer Dielectric Diffraction Grating with Enhanced Laser Damage Threshold

by Duy Thanh Cu, Tien Dat Pham, Vu Tuan Hung Le, Meng Chi Li, Hung Pin Chen and Chien Cheng Kuo

Nanomaterials 2022, 12(12), 1952; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12121952 - 07 Jun 2022

Cited by 3 | Viewed by 2033

Abstract

Diffraction gratings are becoming increasingly widespread in optical applications, notably in lasers. This study presents the work on the characterization and evaluation of Multilayer Dielectric Diffraction Gratings (MDG) based on the finite element method using Comsol MultiPhysics software. The optimal multilayer dielectric diffraction [...] Read more.

Diffraction gratings are becoming increasingly widespread in optical applications, notably in lasers. This study presents the work on the characterization and evaluation of Multilayer Dielectric Diffraction Gratings (MDG) based on the finite element method using Comsol MultiPhysics software. The optimal multilayer dielectric diffraction grating structure using a rectangular three-layer structure consisting of an aluminum oxide Al₂O₃ layer sandwiched between two silicon dioxide SiO₂ layers on a multilayer dielectric mirror is simulated. Results show that this MDG for non-polarized lasers at 1064 nm with a significantly enhanced −1st diffraction efficiency of 97.4%, reaching 98.3% for transverse-electric (TE) polarization and 96.3% for transverse-magnetic (TM) polarization. This design is also preferable in terms of the laser damage threshold (LDT) because most of the maximum electric field is spread across the high LDT material SiO₂ for TE polarization and scattered outside the grating for TM polarization. This function allows the system to perform better and be more stable than normal diffraction grating under a high-intensity laser. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Figure 1

14 pages, 3195 KiB

Open AccessArticle

Mid-Infrared Response from Cr/n-Si Schottky Junction with an Ultra-Thin Cr Metal

by Zih-Chun Su, Yu-Hao Li and Ching-Fuh Lin

Nanomaterials 2022, 12(10), 1750; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12101750 - 20 May 2022

Cited by 6 | Viewed by 1669

Abstract

Infrared detection technology has been widely applied in many areas. Unlike internal photoemission and the photoelectric mechanism, which are limited by the interface barrier height and material bandgap, the research of the hot carrier effect from nanometer thickness of metal could surpass the [...] Read more.

Infrared detection technology has been widely applied in many areas. Unlike internal photoemission and the photoelectric mechanism, which are limited by the interface barrier height and material bandgap, the research of the hot carrier effect from nanometer thickness of metal could surpass the capability of silicon-based Schottky devices to detect mid-infrared and even far-infrared. In this work, we investigate the effects of physical characteristics of Cr nanometal surfaces and metal/silicon interfaces on hot carrier optical detection. Based on the results of scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis, the hot carrier effect and the variation of optical response intensity are found to depend highly on the physical properties of metal surfaces, such as surface coverage, metal thickness, and internal stress. Since the contact layer formed by Cr and Si is the main role of infrared light detection in the experiment, the higher the metal coverage, the higher the optical response. Additionally, a thicker metal surface makes the hot carriers take a longer time to convert into current signals after generation, leading to signal degradation due to the short lifetime of the hot carriers. Furthermore, the film with the best hot carrier effect induced in the Cr/Si structure is able to detect an infrared signal up to 4.2 μm. Additionally, it has a 229 times improvement in the signal-to-noise ratio (SNR) for a single band compared with ones with less favorable conditions. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Figure 1

11 pages, 2840 KiB

Open AccessArticle

Low-Temperature PECVD Growth of Germanium for Mode-Locking of Er-Doped Fiber Laser

by Chun-Yen Lin, Chih-Hsien Cheng, Yu-Chieh Chi, Sze Yun Set, Shinji Yamashita and Gong-Ru Lin

Nanomaterials 2022, 12(7), 1197; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12071197 - 03 Apr 2022

Cited by 7 | Viewed by 2202

Abstract

A low-temperature plasma-enhanced chemical vapor deposition grown germanium (Ge) thin-film is employed as a nonlinear saturable absorber (SA). This Ge SA can passively mode-lock the erbium-doped fiber laser (EDFL) for soliton generation at a central wavelength of 1600 nm. The lift-off and transfer [...] Read more.

A low-temperature plasma-enhanced chemical vapor deposition grown germanium (Ge) thin-film is employed as a nonlinear saturable absorber (SA). This Ge SA can passively mode-lock the erbium-doped fiber laser (EDFL) for soliton generation at a central wavelength of 1600 nm. The lift-off and transfer of the Ge film synthesized upon the SiO₂/Si substrate are performed by buffered oxide etching and direct imprinting. The Ge film with a thickness of 200 nm exhibits its Raman peak at 297 cm⁻¹, which both the nanocrystalline and polycrystalline Ge phases contribute to. In addition, the Ge thin-film is somewhat oxidized but still provides two primary crystal phases at the (111) and (311) orientations with corresponding diffraction ring radii of 0.317 and 0.173 nm, respectively. The nanocrystalline structure at (111) orientation with a corresponding d-spacing of 0.319 nm is also observed. The linear and nonlinear transmittances of the Ge thin-film are measured to show its self-amplitude modulation coefficient of 0.016. This is better than nano-scale charcoal and carbon-black SA particles for initiating the mode-locking at the first stage. After the Ge-based saturable absorber into the L-band EDFL system without using any polarized components, the narrowest pulsewidth and broadest linewidth of the soliton pulse are determined as 654.4 fs and 4.2 nm, respectively, with a corresponding time–bandwidth product of 0.32 under high pumping conditions. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Figure 1

13 pages, 3777 KiB

Open AccessArticle

Highly Reflective Silver-Enhanced Coating with High Adhesion and Sulfurization Resistance for Telescopes

by Hsing-Yu Wu, Shao-Rong Huang, Chih-Hsuan Shih, Li-Jen Hsiao, Hong-Wei Chen, Ming-Chung Cheng and Jin-Cherng Hsu

Nanomaterials 2022, 12(7), 1054; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12071054 - 23 Mar 2022

Cited by 4 | Viewed by 3676

Abstract

Highly reflective metal coatings are essential for manufacturing reflecting telescope mirrors to achieve the highest reflectivity with broad spectral bandwidth. Among metallic materials, enhanced silver-based coatings can provide higher reflectivity in the 400–500 nm spectral range to better performance from visible to near [...] Read more.

Highly reflective metal coatings are essential for manufacturing reflecting telescope mirrors to achieve the highest reflectivity with broad spectral bandwidth. Among metallic materials, enhanced silver-based coatings can provide higher reflectivity in the 400–500 nm spectral range to better performance from visible to near IR. Moreover, over-coating a dielectric protective layer on the mirror’s front side attains additional hardness and oxidation stability. In this paper, we study a combination of thermal and electron beam evaporation as a technology to form protected enhanced high reflective Ag coatings. A newly designed multiplayer film can pass ASTM 5B adhesive performance testing and give sulfurization inhibition. The average specular reflectivity for the enhancement coating is about 98% in wavelengths across the spectral range from 400–1000 nm. This innovation has been demonstrated on a Newtonian type telescope, with storage in an ambiance humidity H = 60–85%, and temperature T = 10–35 °C, for more than six months without degradation in coating performance. Full article

(This article belongs to the Special Issue Applications of Optical Thin Films)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Applications of Optical Thin Films

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (9 papers)

Editorial

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI