Room Temperature Cathodoluminescence Research Articles

Green-emitting cubic GaN/In0.16Ga0.84N/GaN quantum well with 32% internal quantum efficiency at room temperature

Structural and optical properties of a green-emitting cubic (i.e., zinc blende) GaN/In0.16Ga0.84N/GaN single quantum well structure are reported. The active layer is grown on a phase-pure (i.e., 100%) cubic GaN enabled on a 1 × 1 cm2 U-grooved silicon (100) through aspect ratio phase trapping. Energy dispersive x-ray spectroscopy combined with room temperature cathodoluminescence reveals 522 nm green light emission at room temperature with only 16.0% ± 1.6% of indium content, which is ∼30% less than the amount of indium needed in a traditional green-emitting hexagonal (i.e., wurtzite) well. Temperature-dependent behavior of the green emission, such as activation energy, s-shaped peak energy shift, and linewidth, is reported. Cathodoluminescence at 8 and 300 K reveals an internal quantum efficiency of 32.0% ± 0.6%, which is higher than any reported value for cubic wells. Overall, phase-pure cubic active layers on phase transition cubic GaN are shown to be promising for green and longer wavelength emitters.

Branched MgO Nanowires Synthesized by Thermal Evaporation Method in Air at Atmospheric Pressure

MgO nanowires with a branched structure were fabricated using a thermal evaporation method in air at atmospheric pressure. The branched MgO nanowire was made up of two parts: a primary central nanowire trunk and lots of secondary nanowire branches. The branched MgO nanowires had a 4-fold symmetrical structure. The secondary nanowire branches grew perpendicular on the four side facets of the central nanowire trunks with square cross-sections. The nanowire branches also grew in a single row and were vertically well aligned in the same direction with each other. The scanning electron microscopy images of the branched nanowires grown at 1000<sup>o</sup>C showed that the diameter of branches gradually decreased along the growth direction and no catalyst particle was found at the tips of the branches, indicating that the branches were grown by a vapor-solid process. For the branched nanowires grown at 1150<sup>o</sup>C, spherical particles which were shown to be catalysts were observed at the tips of the branches. The chemical analysis by energy dispersive spectroscopy showed that the spherical particles were composed of Mg and O elements. These results suggest that the branches’ growth resulted from a self-catalyzed vapor-liquid-solid process. The structural characterization by X-ray diffraction confirmed that the branched MgO nanowires had a cubic lattice structure. The room temperature cathodoluminescence spectra of the branched MgO nanowires exhibited a very strong visible emission which was associated with oxygen vacancies.

Ultrathin GaN quantum wells in AlN nanowires for UV-C emission

Molecular beam epitaxy growth and optical properties of GaN quantum disks in AlN nanowires were investigated, with the purpose of controlling the emission wavelength of AlN nanowire-based light emitting diodes. Besides GaN quantum disks with a thickness ranging from 1 to 4 monolayers, a special attention was paid to incomplete GaN disks exhibiting lateral confinement. Their emission consists of sharp lines which extend down to 215 nm, in the vicinity of AlN band edge. The room temperature cathodoluminescence intensity of an ensemble of GaN quantum disks embedded in AlN nanowires is about 20% of the low temperature value, emphasizing the potential of ultrathin/incomplete GaN quantum disks for deep UV emission.

Thermal stability of rhombohedral α- and monoclinic β-Ga2O3 grown on sapphire by liquid-injection MOCVD

We investigate the thermal stability of single-phase undoped epitaxial rhombohedral α- and bi-axially-symmetric, monoclinic β-Ga2O3 thin films grown on sapphire substrates by liquid-injection metalorganic chemical vapor deposition (LI-MOCVD) by means of in-situ high-temperature X-ray diffraction (HT-XRD) and room temperature (RT) cathodoluminescence (CL). Ga2O3 layers were vacuum annealed up to 1100 °C, while monitoring the respective 303‾0 and 6‾03 reflections of α- and β-phase Ga2O3. α-Ga2O3 layers were found to withstand the vacuum annealing at 700 °C/20 min, 750 °C/10 min, and 800 °C/8 min without notable degradation, however an indication of reversible biaxial in-plane compressive strain was observed for annealing temperatures close to 800 °C. Annealing at temperatures above 825 °C led to complete layer degradation and partial phase transformation to (010) β-Ga2O3. β-Ga2O3 layers showed no notable degradation or structural changes after the annealing at 1100 °C/30 min, however an indication of reversible biaxial in-plane tensile strain was observed for prolonged annealing at 1100 °C. RT CL spectra revealed the Ga2O3 emission consisted of several distinctive luminescence bands (red, green, blue, and two UV bands). Relatively weak but distinctive signal maxima with energy close to the expected bandgap energies of α- and β-Ga2O3, at 5.3 and 5.0 eV, respectively, were observed and attributed to their near band-edge (NBE) emissions.

Catastrophic optical damage in 808 nm broad area laser diodes: a study of the dark line defect propagation

We present a study of the propagation of dark line defects (DLDs) in catastrophically damaged 808 nm laser diodes, based on cathodoluminescence (CL) measurements and laser mode propagation simulations. Room temperature CL images show blurred DLDs running parallel to the laser cavity. Remarkably, low temperature images reveal their true morphology: the blurred lines are resolved as parallel narrow discontinuous DLDs. This morphology does not match the usually reported molten front scenario of DLD propagation. Low temperature images show that DLDs consist of a sequence of catastrophic optical damage (COD) events separated a few micrometers from each other. Consequently, a different propagation scheme is proposed. The points where the CODs occur suffer a temperature increase and these hot spots play a capital role in the propagation of the DLDs. Their influence on the beam distribution is modelled using finite element methods. The calculations evidence changes on the intensity distribution of the laser that qualitatively reproduce the DLD shapes. Additionally, the COD events result in the generation of defects in the region that surrounds them. The successive CODs in the discontinuous DLDs are rationalized in terms of the enhanced laser absorption in these sensitized regions where the laser beam is concentrated by thermal lensing.

Cathodoluminescence mapping of electron concentration in MBE-grown GaAs:Te nanowires

Cathodoluminescence mapping is used as a contactless method to probe the electron concentration gradient of Te-doped GaAs nanowires. The room temperature and low temperature (10 K) cathodoluminescence analysis method previously developed for GaAs:Si is first validated on five GaAs:Te thin film samples, before extending it to the two GaAs:Te NW samples. We evidence an electron concentration gradient ranging from below 1 × 1018 cm−3 to 3.3 ×1018 cm−3 along the axis of a GaAs:Te nanowire grown at 640 °C, and a homogeneous electron concentration of around 6–8 × 1017 cm−3 along the axis of a GaAs:Te nanowire grown at 620 °C. The differences in the electron concentration levels and gradients between the two nanowires is attributed to different Te incorporation efficiencies by vapor–solid and vapor–liquid–solid processes.

Fabrication of color-toned micro/nanopattern surface by submerged photosynthesis method

Nanosurface patterning can be advantageous for novel opto-electrical devices application. In this study, we utilized the electron beam lithography (EBL) technique to fabricate ZnO nanorods(NRs)/ZnO/Si surface nanopatterning via galvanic submerged photo-synthesis of crystallites (G-SPSC) method, which combines galvanic reactions between two semiconducting surfaces and a photo-induced crystallization in water. By controlling the UV illumination time, high aspect ratio of ZnO NRs were precisely grown on 500 nm size of circular, linear, and lattice patterns. Using bromothymol blue (BTB) gel, a “photo-induced” galvanic reaction was visualized in G-SPSC. Room-temperature photoluminescence (PL) and cathodoluminescence (CL) results dictates oxygen vacancy (VO), ZnO/Si interface luminescence, as well as localized surface plasmon resonance (LSPR) phenomena on the ZnO NRs/ZnO/Si surface. Distinct luminescence behavior was illustrated by color-toned surface patterning (CTSP), opening a possibility for facile fabrication of miniaturized LED application in nanoscale surface area.

Correlation between deep-level defects and functional properties of β-(SnxGa1-x)2O3 on Si photodetectors

Heterogeneous integration of β-(SnxGa1−x)2O3 (TGO) UV-C photodetectors on silicon substrates by molecular beam epitaxy is demonstrated. Multimodal electron microscopy and spectroscopy techniques reveal a direct correlation between structural, compositional, and optical properties of TGO and the functional properties of the photodetectors. Wavelength dispersive x-ray spectroscopy results accurately determine Sn concentrations (x) in the region of 0.020, and room temperature cathodoluminescence (CL) hyperspectral imaging shows changes in the CL emission intensity in TGO compared with a Ga2O3 sample with no Sn. Alloying Ga2O3 with Sn is shown to quench the red emission and enhance the blue emission. The increase in blue emission corresponds to the rise in VGa-related deep acceptors responsible for the high gain observed in the TGO detectors. A Ga2O3 nucleation layer is shown to improve the TGO surface quality and give better device properties compared to TGO grown directly onto the Si substrate, including a higher specific detectivity on the order of 1012 Jones.

Thick AlN Templates By MOCVD for the Thermal Management of III-N Electronics

Ultra-wide bandgap semiconductors have attracted much interest over the last decade. These materials have strong chemical bonding that led to high temperature tolerance, high voltage and power handling capabilities as described by the Baliga figure of merit. Al-rich III-nitride materials are expected to have the best performance over the industry standard Si, and newer options such as SiC and GaN. Continuous improvements dictate the miniaturization of electronic devices, leading to increasingly higher power densities in smaller footprints, leading to heating that causes system failure. Thus, the thermal management is the limiting task for continuous performance scaling. In past we have reported on deep ultraviolet light emitting diodes (LEDs) and AlxGa1-xN (x>0.4) channel Heterojunction Field-Effect Transistors (HFETs) on 2-3 µm thick MOCVD grown high quality AlN/sapphire templates. For template thicknesses over 5 µm either sapphire or AlN patterning is needed to avoid stress related cracking. In this research, we for the first-time report on the direct MOCVD growth and characterization of crack-free, low-impurity AlN templates in excess of 16 μm on basal plane sapphire substrates without doing any external processing. Increasing the thickness improves thermal management and enables an easier sapphire substrate’s laser liftoff for increased DUV light extraction. It would also be used as a heat spreader in power electronics to minimize the operating temperature to maximize power output to industrial loads such as electric vehicles, and large turbines in manufacturing and transportation.All growths were carried out in custom MOCVD reactors with a fast-metalorganic switching manifold using a modified epitaxy procedure in which the Al- and N-precursors (Trimethyl Aluminum and NH3) are pulsed for increased surface mobility. At the initial pulsed growth stage, the growth-temperature and precursor-flow rates are adjusted to yield air-pocketed (voids) rough AlN layers. Most of these high defect materials are located near the AlN/sapphire interface. As the AlN thickness increases in the subsequent growths, the layers turned out smooth and the number of defects is significantly reduced due to dislocation bending/annihilation and cracking is avoided due to strain relief from the voids at the interface. All template growths were carried out at temperatures ~ 1200 - 1300 °C and 40 torr.From X-ray diffraction (XRD), Reciprocal space map (RSM), and Transmission Electron Microscopy (TEM) analysis of these thick AlN templates, we established that they were fully relaxed. Cross-section TEM data clearly shows the presence of voids at ~ 0.4 – 0.9 μm from the AlN/sapphire interface. There is a high density of dislocations present near the void region. Above this region, at least one order of magnitude lower dislocations is observed at the AlN smooth layer region. From the room-temperature Cathodoluminescence (CL) data we see an increase in the band edge emission and a decrease in the defect related long-wavelength signal with increasing AlN template thicknesses. The CL spectra were measured in the edge emission pump geometry on cleaved bars due to the transverse-magnetic polarized nature of the band-edge emission. The monochromatic CL imaging data also confirmed a highly defective region at the AlN/sapphire interface which is also the origin of the long wavelength (below bandgap) CL emission. The Atomic Force Microscopy (AFM) surface scans of the templates showed the surface roughness ~ 0.15 nm to 0.25 nm (for a 5 µm x 5 µm scan). The (102) off axis X-ray linewidths for all these samples ranged from 280 to 330 arc-secs. XRD and Raman experiments confirmed a residual compressive strain in AlN templates compared to the bulk sample. The measured stress ranges from -0.6 GPa to -1.2 GPa for all the templates, reasonable agreement with previous reports. We have found no obvious thickness dependence of the stresses measured from both XRD and Raman, an indication of preserving similar stresses in thick and thin templates.The thermal conductivity of our high-quality 16 µm thick template and the bulk AlN are measured at different temperatures by Time-domain Thermoreflectance (TDTR) technique. The thermal conductivity of the thick AlN at room temperature is 320 Wm-1K-1, or ~10% higher than that of the bulk AlN (~285 W/m-K). At low temperatures (120 K), it exceeds that of bulk AlN by more than 40%. In summary, these templates showed thermal conductivity as high or better than high-cost bulk AlN substrates, demonstrating for the first time that sapphire-based power electronics could be effectively managed thermally. Figure 1

Growth and characterization of cubic GaN grown on GaAs (110) substrate by MOVPE

GaN layers were grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on GaAs (110) substrate at temperature varying in the range of 750–900 °C. 50 nm-thick GaN layer grown at low temperature (550 °C) was used as buffer layer. Scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD) and room temperature cathodoluminescence (RT-CL) studies were carried out and showed a large dependence of the crystalline and optical properties of GaN layer with the growth temperature. A mixture of cubic and hexagonal GaN phases is evidenced by the 2θ/ω spectra which are dominated by a broad peak associated to c-GaN (220) and h-GaN (11.0) reflections. The cubic GaN phase is maximal for a growth temperature of 850 °C. At this temperature, morphological observations by AFM showed the presence of c-GaN islands and RT-CL spectra showed only c-GaN (3.23 eV) emission whereas both emissions of c-GaN (3.23 eV) and h-GaN (3.39 eV) were observed at 900 °C.

Quantitative Assessment of Carrier Density by Cathodoluminescence. I. GaAs Thin Films and Modeling

Doping is a fundamental property of semiconductors and constitutes the basis of modern microelectronic and optoelectronic devices. Their miniaturization requires contactless characterization of doping with nanometer scale resolution. Here, we use low- and room-temperature cathodoluminescence (CL) measurements to analyze p-type and n-type GaAs thin films over a wide range of carrier densities ($2\times 10^{17}$ to $1\times 10^{19}$ cm$^{-3}$). The spectral shift and broadening of CL spectra induced by shallow dopant states and band filling are the signature doping. We fit the whole spectral lineshapes with the generalized Planck's law and refined absorption models to extract the bandgap narrowing (BGN) and the band tail for both doping types, and the electron Fermi level for n doping. This work provides a rigorous method for the quantitative assessment of p-type and n-type carrier density using CL. Taking advantage of the high spatial resolution of CL, it can be used to map the doping in GaAs nanostructures, and it could be extended to other semiconductor materials.

Influence of micro-patterning of the growth template on defect reduction and optical properties of non-polar GaN

We investigate the influence of different types of template micro-patterning on defect reduction and optical properties of non-polar GaN using detailed luminescence studies. Non-polar (or a-plane) GaN exhibits a range of different extended defects compared with its more commonly used c-plane counterpart. In order to reduce the number of defects and investigate their impact on luminescence uniformity, non-polar GaN was overgrown on four different GaN microstructures. The micro-patterned structures consist of a regular microrod array; a microrod array where the −c-side of the microrods has been etched to suppress defect generation; etched periodic stripes and finally a subsequent combination of etched stripes and etched microrods (double overgrowth). Overall the presence of extended defects, namely threading dislocations and stacking faults (SFs) is greatly reduced for the two samples containing stripes compared with the two microrod samples. This is evidenced by more uniform emission and reduction in dark regions of non-radiative recombination in room temperature cathodoluminescence imaging as well as a reduction of the SF emission line in low temperature photoluminescence. The observed energy shifts of the GaN near band edge emission are related to anisotropic strain relaxation occurring during the overgrowth on these microstructures. A combination of stripes and microrods is a promising approach for defect reduction and emission uniformity in non-polar GaN for applications in light-emitting devices as well as power electronics.

Catalyst-Free Thermal Evaporation Synthesis of TiO<sub>2</sub> Nanostructures in Atmospheric Air

TiO<sub>2</sub> nanostructures were synthesized using a thermal evaporation method without a catalyst. TiO powders mixed with graphite powders were used as the source materials. The synthesis process was performed in air atmosphere at 1000 °C. When the mass ratio of TiO/graphite in the source material was 2:1, TiO<sub>2</sub> nanowires and nanobelts started to form. As the mass ratio of graphite to TiO increased to 1:1, TiO<sub>2</sub> nanowires and nanobelts were formed in large quantity. The nanowires had an average diameter of 80 nm and lengths in the range of 3 ~ 11 µm. The average width and length of the nanobelts were 500 nm and 3.4 µm, respectively. However, with further increase in the mass ratio of TiO/graphite to 1:2, no nanostructures were observed. The mass ratio of graphite to TiO in the source material had an important effect on the formation of the TiO<sub>2</sub> nanowires and nanobelts. The X-ray diffraction data confirmed that the TiO<sub>2</sub> nanostructures had a rutile crystal structure. Two emission bands centered at 410 nm and 510 nm were observed in the room temperature cathodoluminescence spectrum of the TiO<sub>2</sub> nanostructures. The emission at 410 nm is attributed to the electron transition from the conduction band to the valence band in rutile TiO<sub>2</sub> crystal, which is indicative of the high crystallinity of the TiO<sub>2</sub> nanostructures.

Optical properties evolution of GaN film grown via lateral epitaxial overgrowth

Spatially resolved Raman scattering mapping and room-temperature cathodoluminescence (CL) mapping of GaN via epitaxial lateral overgrowth (ELOG) on a SiNx-masked GaN template grown on a sapphire substrate were studied. Scanning electron microscope (SEM) measurements show that the ELOG layer is coalesced. Plane view Raman mapping shows that the E2 (high) phonon intensity is stronger in the wing regions than in the window regions. Transmission electron microscopy (TEM) of a cross-section indicates the dislocation annihilation process. Furthermore, the intensity of Raman mapping on a cross-section of A1 (TO) phonon in the coalesced area is more increased than the GaN template. Interestingly, the cross-sectional CL image shows a butterfly shaped pattern that provides a comprehensive understanding of the variations in the point defect distribution during the ELOG GaN regrowth process.

Luminescence behavior of semipolar (101¯1) InGaN/GaN “bow-tie” structures on patterned Si substrates

In this work, we report on the innovative growth of semipolar “bow-tie”-shaped GaN structures containing InGaN/GaN multiple quantum wells (MQWs) and their structural and luminescence characterization. We investigate the impact of growth on patterned (113) Si substrates, which results in the bow-tie cross section with upper surfaces having the (101¯1) orientation. Room temperature cathodoluminescence (CL) hyperspectral imaging reveals two types of extended defects: black spots appearing in intensity images of the GaN near band edge emission and dark lines running parallel in the direction of the Si stripes in MQW intensity images. Electron channeling contrast imaging (ECCI) identifies the black spots as threading dislocations propagating to the inclined (101¯1) surfaces. Line defects in ECCI, propagating in the [12¯10] direction parallel to the Si stripes, are attributed to misfit dislocations (MDs) introduced by glide in the basal (0001) planes at the interfaces of the MQW structure. Identification of these line defects as MDs within the MQWs is only possible because they are revealed as dark lines in the MQW CL intensity images, but not in the GaN intensity images. Low temperature CL spectra exhibit additional emission lines at energies below the GaN bound exciton emission line. These emission lines only appear at the edge or the center of the structures where two (0001) growth fronts meet and coalesce (join of the bow-tie). They are most likely related to basal-plane or prismatic stacking faults or partial dislocations at the GaN/Si interface and the coalescence region.

Suppression of Stark effect in ultra-thin stress-free GaN/AlN multiple quantum well structures grown by plasma-assisted molecular beam epitaxy

We report on suppression of the Stark effect in (1.5-2)-monolayer(ML)-thick (GaN/AlN)100 multiple quantum well (MQW) structures grown on AlN/c-Al2O3 templates by plasma-assisted molecular beam epitaxy. Different stress relaxation mechanisms are revealed in these structures by using a multi-beam optical stress sensor in comparison with the 5ML-MQW structure. The former (with well thicknesses ⩽2MLs) demonstrate the nearly stress-free growth, whereas the latter structure with thicker wells exhibits the slow stress evolution from the high initial compressive stress to the nearly relaxed state with zero stress. Moreover, the former structures demonstrate a bright room-temperature cathodoluminescence (CL) with the single peak at the shortest wavelength 240 nm (1.5ML-QWs), while the latter shows much weaker multi-peak CL spectra in the spectral range of 270-360 nm.

On the photoelectrochemical performances of rare-earth element doped perovskite thin films deposited by PLD

Herein, we report about an anomalous behavior of the photoelectrochemical (PEC) response of Eu-doped BiFeO3 (BEFO) thin films, as a function of the film’s thickness. The aim of the study was to reveal the water splitting potential of doped BFO with rare-earth Eu element. Heterojunction composed of Eu-BiFeO3 and Nb-SrTiO3 (STON) single crystal substrates were fabricated via pulsed laser deposition technique (PLD). By X-ray diffraction, the crystal structures of all deposited thin films were identified as rhombohedral one, with the out-of-plane axis value as a function of film’s thickness. Optical absorption measurements were carried out for the grown films, an indirect and direct band gaps being identified, with the values for both types of bend-gaps depending on the epitaxial strain. The photoelectrochemical behavior (PEC) was analyzed in respect with the thickness of the deposited BEFO layer. To investigate the PEC performance of the fabricated heterojunctions, the photocurrent density ( Jph ) versus bias potential characteristics in-electrolyte PEC setups has been measured. We have found that the photoelectrochemical response was higher for the BEFO samples as compare with the undoped BFO ones. Moreover, the photocurrent density ( Jph ) is almost independent by the film thickness is ranging from 20 nm to 200 nm, while a significant higher photoelectrochemical response is characterizing the heterojunction based on a 180-200 nm thick BEFO films. These anomalous photoelectrochemical response behavior were analyzed in conjunction with the HR-SEM and scanning electron microscopy (SEM) - room-temperature cathodoluminescence (CL) surface imaging analysis.

β-Ga2O3 thin film grown on sapphire substrate by plasma-assisted molecular beam epitaxy

Monoclinic gallium oxide (Ga2O3) has been grown on (0001) sapphire (Al2O3) substrate by plasma-assisted molecular beam epitaxy (PA-MBE). The epitaxial relationship has been confirmed to be [010]( ) β-Ga2O3||[ ](0001)Al2O3 via in-situ reflection high energy electron diffraction (RHEED) monitoring and ex-situ X-ray diffraction (XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum (FWHM) of XRD ω-rocking curve of ( ) plane and root mean square (RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C, respectively. Room temperature cathodoluminescence measurement shows an emission at ~417 nm, which is most likely originated from recombination of donor–acceptor pair (DAP).

Selective area growth of AlGaN nanopyramid arrays on graphene by metal-organic vapor phase epitaxy

Wide-bandgap group III-nitride semiconductors are of special interest for applications in ultraviolet light emitting diodes, photodetectors, and lasers. However, epitaxial growth of high-quality III-nitride semiconductors on conventional single-crystalline substrates is challenging due to the lattice mismatch and differences in the thermal expansion coefficients. Recently, it has been shown that graphene, a two-dimensional material, can be used as a substrate for growing high-quality III–V semiconductors via quasi-van der Waals epitaxy and overcome the named challenges. Here, we report selective area growth of AlGaN nanopyramids on hole mask patterned single-layer graphene using metal-organic vapor phase epitaxy. The nanopyramid bases have a hexagonal shape with a very high nucleation yield. After subsequent AlGaN/GaN/AlGaN overgrowth on the six 101¯1 semi-polar side facets of the nanopyramids, intense room-temperature cathodoluminescence emission is observed at 365 nm with whispering gallery-like modes. This work opens up a route for achieving III-nitride opto-electronic devices on graphene substrates in the ultraviolet region for future applications.

Composition-gradient ZnO/Zn(S,O) heterostructure nanorod arrays and their cathodoluminescence

Well-aligned ZnO/Zn(S,O) heterostructure nanorods have been synthesized through a well-designed chemical vapor deposition synthesis process. The as-synthesized ZnO/Zn(S,O) heterostructures exhibit a single crystal characteristic and a transitive interface with obvious composition gradient. X-ray Energy dispersive spectrometer (EDS) analysis demonstrates that ZnS-phase is rich in the nanorod bottom during the initial nucleation process and the S element content has a drastic decrease along the heterostructure nanorod from the bottom to the top, while O element is spatially detected in the whole rod. Room-temperature cathodoluminescence measurements verify two UV emissions at 330 nm and 385 nm for respective Zn(S,O) and ZnO phases with a strong defect-related emission band in visible range. Finally, the growth mechanism and optical emissions of ZnO/Zn(S,O) heterostructure nanorods are discussed.