Photoluminescence Peak Intensity Research Articles

Effects of High-Temperature Growth of Dislocation Filter Layers in GaAs-on-Si

GaAs-on-Si templates with two different dislocation filter layers (DFLs) were grown at 550 °C low-temperature (LT)-DFL and 660 °C high-temperature (HT)-DFL using metal organic vapor-phase epitaxy and the effects of the growth temperature were studied. The threading dislocation density (TDD) values of LT-DFL and HT-DFL were 5.2 × 107 cm−2 and 1.5 × 107 cm−2, respectively. The 1.5 × 107 cm−2 of TDD in HT-DFL is reduced by almost one order compared to the 1.2 × 108 cm−2 of that in the control sample without DFLs. The annihilation process was mainly observed in the HT-DFL by a transmission electron microscope, resulting in a lower TDD. The 500-nm-thick GaAs bulk layer and InAs QDs were regrown on GaAs-on-Si templates and the optical properties were also evaluated by photoluminescence (PL). The highest PL peak intensity of the HT-DFL indicates that less non-radiative recombination in both the GaAs bulk and QDs occurred due to the reduced TDD. The GaAs p–i–n diodes were also fabricated to analyze the bulk leakage (JB) and the surface leakage current. The JB of HT-DFL shows the lowest value of 3.625 × 10–7 A/cm−2 at applied bias voltage of 1 V, which is 20 times lower than the JB of the control sample without DFLs. This supports that the high-temperature growth of DFL can make a good performance GaAs device on Si.

Role of gas flow direction on monolayer MoS2 growth on patterned surfaces via CVD

The chemical vapor deposition (CVD) technique has been widely used to grow high quality single layer MoS2 crystals. However, there are still issues that need to be clarified in order to determine the appropriate conditions for the repeatable and scalable process. In this study, we experimentally investigated the effect of flow direction on the size distribution and optical signal of monolayer MoS2 flakes grown on microchannel arrayed surfaces. As an important parameter controlling the CVD process, the carrier gas flow was revealed to be highly sensitive to geometric orientation of the patterned surface. The flow direction parallel to the array yielded larger flakes with narrower size distribution, and enhanced photoluminescence (PL) peak intensities compared to the case with flow normal to the array while the Raman intensities for both the cases are almost the same. The size distributions were obtained as 6 ± 13 and 37 ± 4 µm for the perpendicular and parallel cases, respectively. It was also found that the PL peak intensity increased by approximately 1.5 times when switching to parallel configuration. This study presents an experimental approach to understand the influence of the precursor stream reshaped by the growth surface geometry on the structural and optical properties of monolayer MoS2, which has great potential for use in optoelectronic applications.

A Study of the Structural and Surface Morphology and Photoluminescence of Ni-Doped AlN Thin Films Grown by Co-Sputtering.

Aluminum nitride (AlN) is a semiconductor material possessing a hexagonal wurtzite crystal structure with a large band gap of 6.2 eV. AlN thin films have several potential applications and areas for study, particularly in optoelectronics. This research study focused on the preparation of Ni-doped AlN thin films by using DC and RF magnetron sputtering for optoelectronic applications. Additionally, a comparative analysis was also carried out on the as-deposited and annealed thin films. Several spectroscopy and microscopy techniques were considered for the characterization of structural (X-ray diffraction), morphological (SEM), chemical bonding (FTIR), and emission (PL spectroscopy) properties. The XRD results show that the thin films have an oriented c-axis hexagonal structure. SEM analysis validated the granular-like morphology of the deposited sample, and FTIR results confirm the presence of chemical bonding in deposited thin films. The photoluminescence (PL) emission spectra exhibit different peaks in the visible region when excited at different wavelengths. A sharp and intense photoluminescence peak was observed at 426 nm in the violet-blue region, which can be attributed to inter-band transitions due to the incorporation of Ni in AlN. Most of the peaks in the PL spectra occurred due to direct-band recombination and indirect impurity-band recombination. After annealing, the intensity of all observed peaks increases drastically due to the development of new phases, resulting in a decrease in defects and a corresponding increase in the crystallinity of the thin film. The observed structural, morphological, and photoluminescence results suggest that Ni: AlN is a promising candidate to be used in optoelectronics applications, specifically in photovoltaic devices and lasers.

Facile preparation and modification of SrTiO3 through Ni–Cd co-doping as an efficient visible-light-driven photocatalyst

Visible light-driven Ni–Cd co-doped SrTiO3 photocatalyst was prepared through a co-precipitation technique. The influence of various amounts of doped elements on the properties of the pure SrTiO3 phase has been explored. The characterization was performed employing the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscopy (FESEM), UV–visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and transient photocurrent experiments. By Ni–Cd co-doping, the average particle size was reduced from 100 to 65 nm, the band gap value was lowered from 3.2 to 2.78 eV, and the powder's surface area was increased by about 2.3 times compared with the pure phase. Low PL peak intensity, small EIS radius, and higher photocurrent density of the 5 wt% doped sample indicate higher charge transfer efficiency than the pure sample. The effect of different photocatalytic experiment parameters on the photodegradation performance has been studied. In this regard, a 60-min visible light irradiation time, 1 g mL−1 initial dye concentration, and 0.7 g L−1 powder dosage were found to be the best values. After 60 min of visible light irradiation, doped SrTiO3 with 5 wt% Ni–Cd thoroughly degraded methylene blue (MB) dye. Additionally, the superoxide radical and holes also play a significant role in photodegradation as determined by the scavenger trapping test. Compared with MB, the prepared sample demonstrated less degradation ability for methyl orange (MO) and Rhodamine-B (RhB) dyes.

(Digital Presentation) Fabrication of Thick SiGe／Ge Multiple Quantum Wells on Ge-on-Si and Their Optical Properties

We fabricate thick strained Si0.1Ge0.9/Ge multiple quantum wells (MQWs) structures on Ge-on-Si, and evaluate their crystallinities and optical properties. As a result, it is found that highly crystalline Si0.1Ge0.9/Ge MQWs are grown both on Ge-on-Si(100) or Ge-on- Si(111), where surface roughness slightly differs between the two. From both MWQs we obtain strong room-temperature photoluminescence (PL) via quantum confinements of carriers in the MQWs. It is also found that the PL peak positions and intensities are different between (100) and (111). Surface roughening is considered to cause reduction in the PL intensity and the peak shift for the (111) case whereas the MQWs on Ge-on-Si(100) shows very smooth surface and resultantly strong PL intensity, indicating that Si0.1Ge0.9/Ge MQWs are promising for applications to light-emitting devices that can be integrated on the Si platform.

Assessment of the Enhancement for the Excitation Emission in Porous Gan using Photoluminescence

ABSTRACT: This work aims to assess the enhancement of optical properties for porous GaN nanostructures, which fabricated by Photoelectrochemical etching under different current densities. The changing of optical properties for different samples were investigated by Photoluminescence (PL) spectroscopy. A strong near band-gap-edge emission (NBE) was detected with peak energy 3.40 eV for as-grown and sample etched at 5mA/cm2, while its 3.41 and 3.42 eV for samples etched with 10 and 20mA/cm2 respectively. Also, another peak emission from the sapphire substrate at peak 1.7 eV was observed. The PL peak intensity of the porous samples have increased with increasing the porosity, while the FWHM of the near-band-edge peak was decreased in 5 and 10mA/cm2 samples compared to as-grown non-etched sample, indicated that the pore size decreased with etching current density and porosity. Finally, the change of refractive with porosity was investigated in the porous GaN nanostructure.

Low Temperature Photoluminescence Properties of α‐CsPbI 3 Nanocrystals with High Quantum Yield

Temperature-dependent photoluminescence (PL) properties of high quality cubic phase α-CsPbI3 nanocrystals are investigated, and thermal transfer from free excitons to trapped excitons is observed. Free exciton recombination is the main origin of the high PL quantum yield (97%) at room temperature. Little change of PL peak energy is observed with decreasing temperature from 280 to 200 K, and it shifts from 1.84 to 1.81 eV in the region of 200 and 80 K. The PL peak intensity decreases with decreasing temperature first and then increases, and the minimum value is observed at 180 K. Two PL bands are obtained by Gaussian fittings in the PL spectra detected at different temperatures, and the high energy band is attributed to the emission of free excitons, while that for the low energy band is related to the transition of trapped excitons. The PL integrated intensity ratio of trapped exciton and free exciton transition increases from 0.18 to 2.10 with decreasing the temperature, which suggests that thermal transfer from free exciton to trapped exciton states leads to the dominant optical emission of trapped exciton recombination in the low temperature region.

Interaction of Ge(Si) Self-Assembled Nanoislands with Different Modes of Two-Dimensional Photonic Crystal.

The interaction of Ge(Si)/SOI self-assembled nanoislands with modes of photonic crystal slabs (PCS) with a hexagonal lattice is studied in detail. Appropriate selection of the PCS parameters and conditions for collecting the photoluminescence (PL) signal allowed to distinguish the PCS modes of different physical nature, particularly the radiative modes and modes associated to the bound states in the continuum (BIC). It is shown that the radiative modes with relatively low Q-factors could provide a increase greater than an order of magnitude in the integrated PL intensity in the wavelength range of 1.3–1.55 µm compared to the area outside of PCS at room temperature. At the same time, the interaction of Ge(Si) islands emission with the BIC-related modes provides the peak PL intensity increase of more than two orders of magnitude. The experimentally measured Q-factor of the PL line associated with the symmetry-protected BIC mode reaches the value of 2600.

Structural, electrical and optical properties of hetrostructured MoS2/ZnO thin films for potential perovskite solar cells application

ZnO, MoS2, MoS2/ZnO/glass, and ZnO/MoS2/glass thin films have been deposited on glass substrates by chemical bath deposition techniques (CBD). XRD results confirmed the formation of MoS2, ZnO, MoS2/ZnO/glass, and ZnO/MoS2/glass films. All the films have a hexagonal structure. The grain size of heterostructured (MoS2/ZnO/glass and ZnO/MoS2/glass) films is larger than pure (ZnO and MoS2) films. The band gap energy of ZnO, MoS2, MoS2/ZnO/glass and ZnO/MoS2/glass is 3.14 eV, 1.52 eV, 1.62 eV and 2.67 eV, respectively. Photoluminescence (PL) emission peaks of ZnO are observed in the visible region. When ZnO film is deposited on MoS2 film, PL peaks are shifted to smaller wavelengths. A very high PL intensity peak of MoS2 is observed. When MoS2 film was deposited on ZnO film the peak intensity was reduced. The average sheet resistivity of glass/MoS2, glass/ZnO, MoS2/ZnO/glass and ZnO/MoS2/glass films is 6.44 × 104, 7.89 × 103, 5.65 × 104, and 2.45 × 103 (ohm-m), respectively. These materials have potential applications in perovskite solar cells.

Effect of microwave processing on Mn doped ZnO diluted magnetic semiconductor characteristics

5 and 7.5 at% Mn doped ZnO samples were prepared by microwave treatment following thermal curing. The XRD phase analysis reveals the Mn may be present in the unreacted Mn3O4 form or bonded with wurtzite ZnO forming substitutional solid solution (Zn0.99Mn0.01O and Zn0.95Mn0.05O) or spinel (ZnMn2O4). The Fourier transform infra-red (FTIR) band shift to higher wavenumber for the microwave treated samples appearing at 538 and 619 cm−1 indicates formation of ZnMn2O4 spinel structure. Identification of tiny particles in the wall of ZnO lamellae and decrease in Zn2p binding energy signifies vigorous chemical changes taken place on microwave treatment. The structural evolution was depicted by 3d modelling. Quantitative estimation of Mn in the samples was performed by microwave plasma atomic emission spectroscopy (MPAES) and the result matches with the calculated value. Raman spectroscopy shows clear peaks of ZnO, Mn3O4 and MnO2 compounds for all the samples prepared. Whereas, shoulder peak of ZnMn2O4 is observed for 7.5 at% Mn doped microwave pre-treated sample. The optical absorption spectra show major peak near to 360 nm signifying bandgap of ZnO in the visible range. The cation substitution in the host lattice by dopant creates oxygen vacancy (VO) in excess, responsible for increasing bound magnetic polaron, which is clearly evidenced by the presence of broad PL peak near to 535 nm and 548 nm for microwave treated samples. The microwave treatment assists the incorporation of Mn into ZnO lattice as evidenced by reduction of photoluminescence (PL) peak intensity. The magnetic hysteresis loop (B-H curve) of the samples clearly shows increase in saturation magnetisation by ~16.1 and ~24.7 % on microwave treatment of 5 and 7.5 at% Mn doped ZnO respectively.

Gold Nanoparticle-Functionalized Diatom Biosilica as Label-Free Biosensor for Biomolecule Detection.

Diatom biosilica (DBs) is the cell wall of natural diatom called frustule, which is made of porous hydrogenated amorphous silica possessing periodic micro- to nanoscale features. In this study, a simple, sensitive, and label-free photoluminescence (PL) immune-detection platform based on functionalized diatom frustules was developed. Gold nanoparticles (AuNPs) deposited on poly-dopamine-coated diatom frustules via in situ deposition which considerably decreased the intrinsic blue PL intensity of diatom biosilica. Then, goat anti-rabbit immunoglobulin G (IgG) was added to functionalize diatom biosilica-poly-dopamine-AuNPs (DBs-PDA-AuNPs). PL studies revealed that the specific binding with antigen rabbit IgG increased the peak intensity of PL in comparison with the non-complimentary antigen (human IgG). The enhancement in PL intensity of DBs-PDA had a linear correlation with antigen (rabbit IgG) concentration, whose limit of detection (LOD) reached 8 × 10-6 mg/ml. Furthermore, PL detection based on DBs-PDA-AuNPs showed a high detection sensitivity with the LOD as low as 8 × 10-9 mg/ml and spread over almost eight orders of magnitude, making it suitable for the sensitive quantitative analysis of immune complex compared with traditional fluorescence immunoassay. Hence, the study proves that the AuNP-functionalized diatom frustules can serve as an effective biosensor platform for label-free PL-based immunoassay.

Annealing effect on SiNx/SiO2 superlattice with ultrathin sublayer fabricated using plasma-enhanced atomic layer deposition

Because of the precise control of film thickness, atomic layer deposition (ALD) offers significant advantages in fabricating high-quality superlattice films. For the first time, a SiNx/SiO2 superlattice with an ultrathin SiNx sublayer layer (1.5 nm) and a SiO2 barrier layer (3 nm) was successfully fabricated using plasma-enhanced ALD. Transmission electron microscopy (TEM) measurements demonstrate the maintenance of multilayer structures with smooth interfaces. Next, the annealing effect on the microstructural, optical, and chemical properties of these SiNx/SiO2 superlattice structures was thoroughly investigated. With increasing annealing temperature, X-ray reflection (XRR) and TEM measurements revealed consistent changes in interface, morphology, roughness, density, and thickness. After high-temperature annealing, Fourier-transform infrared spectroscopy (FTIR) measurements combined with X-ray photoelectron spectroscopy (XPS) measurements revealed significant reductions in Si–H-related defects and absorption bands. Photoluminescence (PL) was used to characterize the light emission property, and it was discovered that increasing the annealing temperature decreased the PL peak intensity at ∼550 and 900 nm. The silicon nanocrystals (Si–NCs)-related PL peak (∼900 nm) became dominant as the annealing temperature increased. The findings in this paper shed light on the annealing effect on the new superlattice material prepared via ALD. Improved PL properties of this type of superlattice are expected and can be obtained in future research by optimizing the ALD deposition process and annealing parameters.

Room temperature luminescence and ferromagnetism from transition metal ions: Mn-, Co- and Ni-doped ZnS nanoparticles

ZnS nanoparticles (NPs) and transition metal ions (TMIs) doped ZnS NPs were synthesized by the chemical precipitation method facile via aqueous CTAB micelles. The structural properties, crystallography, morphology, composition analysis, photoluminescence (PL), and magnetic properties of samples were characterized by Fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD) analysis, Field emission scanning electron microscope (FESEM), Energy dispersive X-ray (EDX) spectroscopy, Fluorescence spectroscopy, and Vibrating sample magnetometer (VSM). All the synthesized NPs exhibited a cubic zinc-blende single-phase crystal structure with crystallite size in 2–8 nm range, which indicates the TMIs ions substituted the lattice site of Zn2+ ions, due to almost similar ionic radii of Zn2+ and TMIs (Mn2+, Co2+, and Ni2+), i.e., 0.074, 0.083, 0.069, and 0.065 nm, respectively. PL peak intensity enhanced with TMIs doping causes an excited state to the ZnS NPs, resulting in PL spectra turning into the visible region. ZnS NPs show mixed dominant diamagnetic and weak ferromagnetic behavior. TMIs ions doped ZnS NPs show the well-defined ferromagnetic behavior at room temperature (RT).

Internal Referencing Photoluminescence Probes for Simultaneous Sensing of O2 Gas and Temperature Based on Mn:MAPb(Br/Cl)3 Perovskite

The ratiometric photoluminescence (PL)‐based O2 sensitive probes provide built‐in self‐calibration for the correction of various target‐independent influencing factors. They attract particular attention to be used for O2 gas sensing and imaging. Herein, internal referencing ratiometric PL probes are fabricated that not only detect O2 concentration and temperature simultaneously but also remove the destructive effect of temperature on O2 sensing. A dual‐emission thin film of Mn‐doped halide perovskite nanocrystals (PNCs) (Mn:MAPb(Br/Cl)3) with a 50% PL quantum yield is used as the sensing layer, which is synthesized in situ. Through the sensing process, excitonic PL and the PL caused by Mn are used for detecting temperature and O2 partial pressures, respectively. Remarkably, the Mn PL intensity shows 40% decrement with increasing O2 partial pressures from 0% to 20%, while for the excitonic PL, intensity changes are less than 5%. As the temperature undesirably affects the sensing quantity, the O2 PL is used as an internal reference signal to achieve good accuracy and selectivity. Furthermore, the temperature variation is determined by measuring PL peak intensity change and wavelength shift. In addition to the O2 gas sensitivity of 1.55, a relative temperature sensitivity of −9.36% K−1 is also achieved.

Spectroscopic, structural, and strain-dependent analysis of suspended bulk WSe2 sheets

Among the two-dimensional transitional metal dichalcogenides, tungsten diselenide (WSe2) has recently attracted a great deal of interest because of its interesting optoelectronic properties, which makes it well-positioned for a variety of electronic and quantum-optoelectronic applications. In this work, Raman spectroscopy and photoluminescence (PL) spectroscopy were utilized to analyze the phononic and electronic parameters in suspended bulk WSe2 sheets, fabricated utilizing photolithography and wet chemical etching. The optical properties such as the PL peak intensities were found to be enhanced by almost ∼4× in the suspended WSe2 regions when compared to substrate supported bulk WSe2. Additionally, temperature T-dependent Raman spectroscopy was conducted to calculate the first-order Raman temperature coefficient χ, which was determined to be lower in the suspended bulk WSe2 sheets due to the absence of substrate-induced scattering. Finally, we analyzed the modulation of Raman and PL peaks with local strain engineering from which the sensitivity of the Raman-active E2g1 mode and PL indirect I-peak in suspended bulk WSe2 were also calculated. Our work will be beneficial in analyzing thermal, optical, and mechanical properties of WSe2 in a suspended platform for its application in electronic, thermoelectric, and mechanical sensors in the future.

Effect of bismuth surfactant on the structural, morphological and optical properties of self-assembled InGaAs quantum dots grown by Molecular Beam Epitaxy on GaAs (001) substrates

In this work, we have investigated the effect of Bi surfactant on structural, morphological and optical properties of 5 monolayers self-assembled InGaAs quantum dots (QDs) grown on GaAs (001) substrates at various growth temperatures (435, 467 and 495 °C) by Molecular Beam Epitaxy. Two types of InGaAs QDs samples grown with and without exposure to bismuth were studied using Atomic Force Microscopy, Scanning Electron Microscopy, Transmission Electron Microscopy and Photoluminescence (PL). Our results have demonstrated that Bi-mediated growth provides improved control of several properties of InGaAs QDs including an enhancement of the QD PL peak intensity by 1.7 times as compared to InGaAs/GaAs control sample grown without Bi. In addition, a red-shift of the PL peak energy of about 40 meV was also observed when the InGaAs QDs were grown by using Bi evidencing that Bi surfactant affects considerably the size of QDs. Furthermore, the QDs grown with Bi surfactant exhibited a higher degree of size uniformity as demonstrated by the observation of narrower Full Width at Half Maximum (FWHM) of the PL peaks. We have also shown that both Bi surfactant and substrate temperature play an important role to control the density of InGaAs QDs. The QD density decreased from 8.9 × 1010 cm−2 (control sample) to 2.0 × 1010 cm−2 for the sample grown at the lowest temperature of 435 °C under Bi flux. All these approaches to control and improve the properties of self-assembled QDs are important for device applications that require high optical efficiency and low QD density.

Characterization of Mechanochemical Modification of Porous Silicon with Arginine

Mechanochemistry initiated the reaction of hydrogen-terminated porous silicon (H/por-Si) powder with arginine. Samples were analyzed using Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. Arginine, which was physisorbed onto the surface of por-Si, blue-shifted the peak PL intensity from ~630 nm for the H/por-Si to ~565 nm for arginine-coated por-Si. Grinding for 4 h reduced >80% of the initially 2–45 µm particles to <500 nm, but was observed to quench the PL. With appropriate rinsing and centrifugation, particles in the 100 nm range were isolated. Rinsing ground powder with water was required to remove the unreacted arginine. Without rinsing, excess arginine induced the aggregation of passivated particles. However, water reacted with the freshly ground por-Si powder producing H2. A zeta potential of +42 mV was measured for arginine-terminated por-Si particles dispersed in deionized water. This positive value was consistent with termination such that NH2 groups extended away from the surface. Furthermore, this result was confirmed by FTIR spectra, which suggested that arginine was bound to silicon through the formation of a covalent Si–O bond.

The investigation of photoluminescence properties in InxGa1-xN/GaN multiple quantum wells structures with varying well number

The photoluminescence (PL) properties of InGaN/GaN multiple quantum wells (MQWs) samples with a different quantum well number (two, three, and four) grown by molecular beam epitaxy have been studied in the temperature range between 3 and 300 K. The redshift-blueshift-redshift in the PL peak energy of InGaN well, which is known that as S-shaped behavior, is observed with increasing temperature in the investigated samples. S-shaped behavior is associated with carrier localization states and inhomogeneity in InGaN/GaN MQWs samples. This behavior is explained with the theoretical band tail model. The parameters showing the effect of carrier localization degree are determined and discussed in detail. Furthermore, it is presented the activation energy of charge carriers by using InGaN related-normalized PL peak intensity as a function of the reverse of temperature and Arrhenius function for all samples. The highest PL intensity is obtained in sample B with 3-QWs. Determining carrier localization effect and activation energy plays a vital role in luminescence efficiency and quality of InGaN/GaN MQWs devices.

Growth and Fabrication of GaAs Thin-Film Solar Cells on a Si Substrate via Hetero Epitaxial Lift-Off

We demonstrate, for the first time, GaAs thin film solar cells epitaxially grown on a Si substrate using a metal wafer bonding and epitaxial lift-off process. A relatively thin 2.1 μm GaAs buffer layer was first grown on Si as a virtual substrate, and a threading dislocation density of 1.8 × 107 cm−2 was achieved via two In0.1Ga0.9As strained insertion layers and 6× thermal cycle annealing. An inverted p-on-n GaAs solar cell structure grown on the GaAs/Si virtual substrate showed homogenous photoluminescence peak intensities throughout the 2″ wafer. We show a 10.6% efficient GaAs thin film solar cell without anti-reflection coatings and compare it to nominally identical upright structure solar cells grown on GaAs and Si. This work paves the way for large-scale and low-cost wafer-bonded III-V multi-junction solar cells.

Phase and microstructure control of electrodeposited Manganese Oxide with enhanced optical properties

Mn3O4 and Mn2O3 were synthesized by potentiostatic electrodeposition from a de-aerated manganese acetate and sodium sulfate electrolytic bath, followed by annealing. The electrodeposition parameters (including applied potential, precursor concentration, pH, temperature) and the thermal treatment conditions were investigated to obtain the best control over microstructure and stoichiometry of manganese oxides. We found that the applied voltage is the key parameter affecting the valence state of initial amorphous manganese while the thermal treatment leads to crystallization and tuning of optical properties without substantially changing the morphology. The as-electrodeposited manganese oxides are X-rays amorphous, while two different crystalline phases, Mn3O4 and Mn2O3, were obtained after the thermal treatment depending on the applied voltage. Through the analysis of TEM cross section images, a fiber-like growth was observed for Mn3O4, while Mn2O3 presented a less porous-more compact microstructure. The optical properties were investigated, resulting in an enhancement in the charge separation properties of the thermally treated manganese oxides, reflected by nearly a 40 % reduction in the photoluminescence peak intensity. We believe that these finding will be useful in the future development of environmental friendly manganese oxide-based photoelectrochemical systems.