Pulsed Laser Deposition Thin Films Research Articles

The use of He buffer gas for moderating the plume kinetic energy during Nd:YAG-PLD growth of EuxY2−xO3 phosphor films

We have investigated the He buffer gas process of moderating the kinetic energy of the pulsed laser deposition (PLD) plume during EuxY2−xO3 phosphor film growth. When using a neodymium yttrium aluminum garnet laser for PLD thin film growth, the kinetic energy of the ablation plumes can be high enough to cause the formation of point defects in the film. The buffer gas pressure is an important process parameter in PLD film growth. We find that the presence of the He buffer gas reduces the kinetic energy of the laser deposition plume through many low-angle collisions in the gas phase by a factor of 7 without reducing the deposition rate. This is because He is much lighter than any of the elements in the plume and it does not affect the composition of the oxide films. Consequently, the resputtering of the Y2O3 film surface by the plume was significantly suppressed in the presence of the He gas moderator, leading to a decrease of the defect density in the Y2O3 films. The improvement of the film quality was verified by a systematic analysis of time-resolved photoluminescence (PL) data for EuxY2−xO3 composition–gradient films. The PL lifetime and intensity of Eu0.2Y1.8O3, which shows the highest PL intensity, increased by 13.3% and 36.4%, respectively, when the He gas moderation process was used. The He buffer gas process is applicable to the PLD growth of the other oxide materials as well, where the reduction of the kinetic energy of the plume would bring the PLD process closer to the molecular beam epitaxy growth condition.

Physical properties of LaBO3 (B = Mn, Fe, Co) thin films grown on SrTiO3 by pulsed laser deposition technique

Realizing an oxide thin film with proper stoichiometry is one of the most challenging objects in materials science. Owing to the growth dynamics as well as kinetics, the physical properties of thin films often differ from their bulk counterparts. Here, we report pulsed laser-deposited thin films of LaBO3 (B = Mn, Fe, Co) grown on a SrTiO3 (001) substrate under various thermodynamic conditions. Structural, magnetic, and optical studies have been carried out. The x-ray diffraction study confirms that an appropriate choice of growth thermodynamics may help one to realize epitaxially grown films on the SrTiO3 substrate with out-of-plane lattice parameters 3.976, 3.984, and 3.825 Å for LaMnO3 (LMO), LaFeO3 (LFO), and LaCoO3 (LCO), respectively. A mixed valence state of Mn2+, 3+, 4+ for LMO, a Fe3+ state for LFO, and a mixed state of Co2+, 3+ for LCO have been confirmed by x-ray photoelectron spectroscopy, which is in good agreement with the Ellingham diagram. The optical study showed a bandgap of 1.2, 2.5, and 1.5 eV for LMO, LFO, and LCO, respectively. Ultraviolet photoelectron spectroscopy (UPS) shows a glimpse of the valence band maximum and Fermi level position. UV, UPS, and photoconductive study simultaneously results in a type II band bending, i.e., staggered type bending is observed at these interfaces. Room temperature weak ferromagnetism along with the insulating nature and a sign of photovoltaic application of these thin films fascinate to carry forward rigorous study from fundamental as well as technological points of view.

Influence of doping concentration and annealing temperature on the structure, particle morphology, and luminescent properties of powders and pulsed laser deposited thin films of bismuth-doped lanthanum gallate

Bi3+ doped LaGaO3 powders and thin films were grown via citric acid sol-gel combustion method and pulsed laser deposition (PLD) technique, respectively. X-ray diffraction data confirmed crystallization of the orthorhombic LaGaO3 phase. Inductive coupled plasma spectroscopy data indicated that some Bi3+ ions evaporated at temperatures exceeding 800 °C during thermal treatment. The highest photoluminescence (PL) and cathodoluminescence (CL) emissions with a peak stabilized at 370 nm were observed from La1-x GaO3:Bi3+x=0.003 powders annealed at 1200 °C. The PL and CL emission spectra of La1-x GaO3:Bi3+x=0.003 PLD thin films were similar to those of the powder samples. The effect of Bi3+ concentration and annealing temperature on the properties of powders and thin films is discussed.

Nd:YAG infrared laser as a viable alternative to excimer laser: YBCO case study

We report on the growth and characterization of epitaxial YBa_{2}Cu_{3}O_{7-delta } (YBCO) complex oxide thin films and related heterostructures exclusively by Pulsed Laser Deposition (PLD) and using first harmonic Nd:Y_{3}Al_{5}O_{12} (Nd:YAG) pulsed laser source (lambda = 1064 nm). High-quality epitaxial YBCO thin film heterostructures display superconducting properties with transition temperature sim 80 K. Compared with the excimer lasers, when using Nd:YAG lasers, the optimal growth conditions are achieved at a large target-to-substrate distance d. These results clearly demonstrate the potential use of the first harmonic Nd:YAG laser source as an alternative to the excimer lasers for the PLD thin film community. Its compactness as well as the absence of any safety issues related to poisonous gas represent a major breakthrough in the deposition of complex multi-element compounds in form of thin films.

Photoluminescence, cathodoluminescence degradation and surface analysis of Gd2O3:Bi pulsed laser deposition thin films

Gd2-xO3:Bix = 0.003 thin films were successfully deposited on Si (100) substrates in vacuum and an oxygen atmosphere at different substrate temperatures using the pulsed laser deposition technique. The microstructure, surface topography, chemical composition analysis and luminescent properties of the samples were studied. The influence of prolonged electron beam exposure on the surface state, chemical and cathodoluminescence (CL) stability of the samples was investigated. The background atmosphere and substrate temperature were found to significantly affect the microstructure and photoluminescence (PL). According to scanning electron microscopy cross-sections, the thicknesses for the thin films were relatively constant around 100 nm. The CL emission intensity degradations in a vacuum and an oxygen atmosphere were checked synchronously with the Auger peak-to-peak heights using the same electron beam for both measurements. The effect of the electron bombardment on the surface state of the samples was studied by using Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). All major elements (gadolinium and oxygen) were located, with additional carbon and chlorine that were removed during the early stages of electron bombardment. Generally, the CL intensity of the thin films with a blue-green emission was stable under electron bombardment, indicating that this phosphor may be appropriate for field emission displays applications.

Understanding the effects of electric-field-induced phase transition and polarization loop behavior on the energy storage performance of antiferroelectric PbZrO3 thin films

Antiferroelectric PbZrO3 (PZO) thin-films were fabricated by pulsed laser deposition (PLD) and sol-gel techniques to investigate the effect of antiferroelectric-ferroelectric (AFE-FE) phase transition on the energy storage performance. The (100)-oriented PLD thin-films have a square-double polarization-electric field (P-E) hysteresis loop with a sharp-phase transition and the (111)-oriented sol-gel thin-films have a slanted P-E loop with a diffused-phase transition. The difference in the phase transition fields between PLD and sol-gel thin-films could be attributed to their difference in crystalline orientations. In this case, the antipolar AFE phase is along the [110]-direction of the original tetragonal-cell under zero electric-field, while the antipolar AFE phase switches into the polar FE phase under a strong enough electric-field and the tetragonal-cell becomes rhombohedral with the polar direction of [111]. Due to the larger maximum polarization and slimmer P-E loop, the higher recoverable energy-storage (Ureco) of 19.4 J/cm3 and larger energy-efficiency (η) of 70.8%, are achieved in sol-gel thin-films. More importantly, this film shows excellent charge-discharge cycling endurance of both Ureco and η values after 1010 cycles and good thermal-stability under a wide operating temperature. From the viewpoint of applications, the sol-gel method is considered to be a promising approach towards producing low-cost PZO thin-films for high-efficiency energy-storage devices over a broad temperature range.

Studies on piezo coefficients of PLD and sol-gel grown PZT thin film for devices

The effect of electrical (DC) contact poling processes on the ferroelectric and piezoelectric properties of sol–gel and pulsed laser-deposited PZT thin films has been investigated as a function of the poling field, temperature and time. The remnant polarization and piezoelectric coefficient are found to increase with and saturate at dc-poling field of 100- 300 kV/cm, temperature of 100–120 °C and poling time of 10–20 min. as compared with un-poled PZT thin films. The P-E hysteresis loops of poled PLD grown PZT films shows sharper switching behaviour as compared to imbalanced loop in sol-gel grown films. An improvement of piezoelectric and ferroelectric properties of sol–gel PZT thin films is found, as compared to those deposited using pulsed laser deposition (PLD), indicating that a poling process is required for sol–gel PZT thin films.

Effect of substrate temperature and post annealing temperature on ZnO:Zn PLD thin film properties

The pulsed laser deposition (PLD) substrate temperature and post-annealing temperature are effective methods to control the film optical and structural properties. The structure, morphology and optical properties of the deposited and post-annealed PLD ZnO:Zn films were studied. The films were deposited at different substrate temperatures of 50 °C, 200 °C and 400 °C. The films deposited at the substrate temperature of 50 °C and 200 °C were post-annealed in air at 400 °C and 600 °C for two hours. The films all had a highly preferential orientation with the hexagonal c-axis perpendicular to the substrate surface. The stress was found to be compressive stress with values −3.289 GPa, −4.864 GPa and −4.425 GPa for the film deposited at 50 °C, 200 °C and 400 °C, respectively. After post-annealing treatments, the stress of the films was almost completely released and stress-free films were obtained. The crystallite sizes were 19 nm, 25 nm and 39 nm, while the average particles sizes were 95 nm, 85 nm and 129 nm for the film deposited at 50 °C, 200 °C and 400 °C respectively. The crystallite sizes and particles sizes seemed to increase with the increase in the substrate temperature. Contrary to this, the change in crystallite sizes were inversely proportional to the particles size when increasing the post-annealing temperatures. Deconvoluted X-ray photoelectron spectroscopy peaks of the O1s binding energy region revealed that the films deposited at different substrate temperatures contained oxygen-related defects. Photoluminescence studies revealed that the films all emitted ultra-violet emission around 379 nm. The film deposited at 50 °C emitted a broad green emission centered at ∼524 nm. By increasing the substrate temperature up to 200 °C and 400 °C a new orange emission around 621 nm and 634 nm as well as a weak emission around 416 nm and 500 nm were observed, respectively. After post-annealing treatments, new bands over the visible region (blue, green and orange-red) were observed, the orange-red emissions at ∼ 626 nm to 681 nm being dominant for the annealed samples. The defects-related visible emission was discussed in detail and it was in good agreement with previous studies.

Grain Boundary Design Deduced from Epitaxial Pulsed Laser Deposition Thin Film Electrode for Long Life Polycrystalline Cathode Particles

Polycrystalline cathode active materials in lithium-ion batteries have superior potential response. In order to achieve a longer battery life, it is necessary to prevent the polycrystalline particles from cracking during charge/discharge cycling. An investigation into the interfacial reactions, especially the side reactions at the grain boundary, is presented here to realize highly stable cathode-active polycrystalline particles. We propose that the formation of a resistive solid electrolyte interphase (SEI) by interfacial side reactions leads to volume expansion of the grain boundary, consequently causing the cracking of polycrystalline particles. An example of using grain boundary modification to prevent cracking during charge/discharge cycling is discussed. An epitaxial thin film electrode of (104)-oriented Li(Ni,Co,Mn)O2 cathode-active material with surface modification was prepared using pulsed laser deposition (PLD), in order to investigate how to protect the grain boundaries of cathode particle products. Several effective modifications were observed to suppress both resistive film formation in the grain boundary and the crystal structure destruction of cathode materials. These modifications prevented particle cracking in spite of the crystal volume change during repeated Li+ inter/de-intercalation. Cracking causes the internal resistance of the particles to increase, resulting in capacity fading of the battery. The cross section of deteriorated cathode electrodes shows a notable degree of cracking growth along the grain boundaries of the cathode active particles. Nano secondary ion mass spectroscopy (NanoSIMS) was carried out to confirm the elemental composition at the grain boundaries. The NanoSIMS analysis revealed that the cracks are filled with a typical resistive SEI, which contained species such as lithium alkyl carbonate and lithium fluoride. Although these components are known byproducts formed on the particle surface, it is notable that the reaction field extends into the grain boundaries. Boundary cracking is often discussed as a consequence of lattice expansion during electrochemical Li+ de-intercalation. However, lattice expansion also has the benefit of improving ionic conduction due to the expansion of Li+ diffusion path in the lattice. Therefore, it is important to develop polycrystalline particles that do not crack with permissible degree of volume change in the crystals. In order to study the efficient protection of the grain boundary from the resistive byproduct generation, epitaxial thin film electrodes oriented in the (104) crystal plane were prepared using PLD technique based on a previous work [1]. A protective film coating was then deposited on the surface of one thin electrode. A comparison of charge/discharge cycling tests for electrodes with and without protective coating shows a clear difference in the capacity and resistive film formation. Almost no resistive SEI was generated on the coated electrode, while thick SEI growth was observed on the pristine electrode, as shown in Figure 1. Moreover, the protective coating was effective in maintaining both the original electrochemical capacity and the crystal structure. Based on these results, another experiment was performed to modify the grain boundaries of the product level cathode-active particles with practical technique. The composition introduced in the grain boundaries was confirmed with NanoSIMS measurement. The particles with a modified grain boundary showed superior charge/discharge cycling performance. The cross section of the particles shown in Figure 2 is well consistent with the aforementioned PLD model experiment, where neither cracking nor SEI growth was observed along the particle grain boundaries. Thus, we have proven that epitaxial thin film electrodes are useful not only for theoretical studies but also for practical applications. The method described here can be used to suppress undesired interfacial reactions at the grain boundary in cathode active materials. [1] K. Sakamoto, M. Hirayama, N. Sonoyama, D. Mori, A. Yamada, K. Tamura, J. Mizuki, and R. Kanno, Chem. Mater. 21 (2009) 2632. Figure 1

Effect of Fe and Ni nanoparticles on the structure and mechanical properties of alumina thin films

Abstract This paper discusses the synthesis and characterization of Al 2 O 3 /Fe and Al 2 O 3 /Ni nanocomposite thin films formed by embedding Fe or Ni nanoparticles into alumina matrix using pulsed laser deposition (PLD), RF and pulsed DC magnetron sputtering techniques. The effect of nanoparticle dispersion and temperature on the phase, structure and mechanical properties of the nanocomposite thin films were studied using grazing incidence X-ray diffraction (GIXRD), high resolution transmission electron microscopy (HRTEM) and nanoindentation respectively. The GIXRD and HRTEM studies revealed that dispersion of metal nanoparticles into alumina matrix promoted partial crystallization of Al 2 O 3 at lower temperatures. The nanoindentation results showed an increase in hardness of the nanocomposite which was dependent on temperature and the metal content. The hardness of Al 2 O 3 /Fe nanocomposite thin films was observed to be in the range of 15 GPa–29 GPa for PLD thin films, 16.5 GPa–22.5 GPa for RF magnetron sputtered thin films and 11 GPa–16 GPa for pulsed DC sputtered thin films. The nanoindentation results also showed that the hardness of Al 2 O 3 /Ni deposited by PLD ranges from 15 GPa to 28 GPa.

TOF SIMS induced artificial topographical effects on the Y2(Al,Ga)5O12:Tb3+ thin films deposited on Si substrates by the pulsed laser deposition technique

Abstract The presence of various types of particles on the surface of the pulsed laser deposited (PLD) thin films as well as the differences in the film structure, played an important role to induce artificial topographical effects on Y3(Al,Ga)5O12:Tb3+ PLD thin films deposited on Si substrates measured by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). The two and three-dimensional (2D and 3D) images have been recorded in the positive ion mode. Analysis of the 3D images shows big agglomerated particles on the surface of the Si substrate that appears to be embedded in the substrate and the substrate appears to be on the same level as the particles. This phenomenon is due to the artificial topographic effects which are attributed to the experimental setup of the TOF-SIMS system.

Pulsed laser deposition in Twente: from research tool towards industrial deposition

After the discovery of the perovskite high Tc superconductors in 1986, a rare and almost unknown deposition technique attracted attention. Pulsed laser deposition (PLD), or laser ablation as it was called in the beginning, became popular because of the possibility to deposit complex materials, like perovskites, as thin film. By introducing in situ diagnostics and control of the laser fluence, PLD became a technique for several experimental studies of diverse complex materials. Nowadays, first steps towards industrial applications of PLD thin films on large wafers, up to 200 mm, are underway. In this paper we give a brief overview of the progress that PLD has made in our research group in Twente. Starting with control of deposition parameters, via in situ diagnostics with reflection high-energy electron diffraction and ending with the latest development in equipment for large-area deposition.

Optical and structural characterization of pulsed laser deposited ruby thin films for temperature sensing application

The ruby thin films were deposited by pulsed laser deposition (PLD) technique in an atmosphere of oxygen using ruby pellet, indigenously prepared by mixing Al2O3 and Cr2O3 in appropriate proportion. The characteristics R1 and R2 lines at 694.2nm and 692.7nm in the photoluminescence spectra of target pellet as well as that of PLD thin films, confirmed the ruby phase in both. The XRD and Raman spectra confirmed deposition of c-axis oriented crystalline ruby thin film on sapphire substrate. Effect of deposition time, substrate and deposition temperature on PLD grown thin films of ruby are reported. The intensity of R1 and R2 lines of PLD ruby thin films increased enormously after annealing the film at 1000°C for 2h. The film deposited on sapphire substrate for 2h was 260nm thick and the corresponding deposition rate was 2.16nm/min. This film was subjected to temperature dependent photoluminescence studies. The peak positions of R1 and R2 lines and corresponding line width of PLD ruby thin film were observed to be blue shifted with decrease in temperature. R1 line position sensitivity, dν¯/dT, cm−1/K in the range 138–368K was very well fitted to linear fit and hence can be used as temperature sensor in this range.

Molybdenum thin films via pulsed laser deposition technique for first mirror application

AbstractMirror like Molybdenum thin films on SS substrate in vacuum (10−3Pa) and in Helium environment has been achieved by Pulsed Laser Deposition (PLD) Technique. The PLD thin films of Molybdenum have been characterized by using X-ray Diffraction (XRD) pattern, Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Energy Dispersive X-ray (EDX). The specular reflectivity was recorded with Fourier Transform Infra-Red spectrometer and UV-Visible spectrometer. The optical quality of the thin films was tested via interferometric technique. At the optimum deposition parameters, the crystal orientation was in Mo(110) phase. The FIR-UV-Visible reflectivity of the mirror was found to be closed to that of the polished bulk Molybdenum and Stainless Substrate (SS) substrate.

Domain evolution in lead-free thin film piezoelectric ceramics

Due to environmental and health concerns lead-free piezoelectric systems are currently being evaluated for use as replacements for lead-based ceramics. (1-x)Na0.5Bi0.5TiO3 – xBaTiO3 (NBT-xBT) is a promising alternative. In order to develop materials with improved performance, it is necessary to understand local structure effects on the piezoelectric response at the grain level. Using piezoresponse force microscopy (PFM), we have studied the domain evolution under locally applied electric fields. Using pulsed laser deposition thin films are deposited on Pt/Ti/SiO2/Si substrates at a temperature of 650 °C in a 150 mTorr O2 environment. In NBT-0.05BT films, domains are clearly visible after the application of a bias field and they relax after a period of time. After the films are exposed to ambient conditions for several weeks, they must be annealed before domains are again visible with PFM. Domain images after poling indicate that the polarization direction is rotating in the plane of the sample.

Optimization of the ${\rm BaCeO}_{3}$ Concentration in YBCO Films Prepared by Pulsed Laser Deposition

A series of studies has been carried out on thin films prepared by pulsed laser deposition (PLD) from micro-grained targets of YBa2Cu3O7-x (YBCO) to determine the effect of doping them with BaCeO3 (BCO) in concentrations between 0-10 wt%. BCO has been found to increase Jc in e.g. melt-textured and bulk samples, but no systematic study with PLD thin films has been performed. Magnetometric measurements up to 8 T and down to 10 K as well as structural measurements with XRD and AFM were performed. Jc increased with doping and the highest Jc 's were achieved with low dopant levels (2% and 4%), which varied according to the external field and temperature. Tc decreased when the dopant concentration was increased, similarly as in BaZrO3 (BZO) doped films. However, the BCO growth process in the films was found to be different from the BZO and, furthermore, an interesting effect where the YBCO twin structure is altered was found around 6 wt% of BCO. The Jc results and a comparison with structural properties with increasing dopant level and optimally BZO-doped YBCO thin films are presented.

Yttria-stabilized zirconia thin films deposited by pulsed-laser deposition and magnetron sputtering

Yttria-stabilized zirconia (YSZ, ZrO2:Y2O3) was deposited on (100) silicon by two physical vapor deposition techniques: pulsed laser deposition (PLD) and reactive magnetron sputtering (RMS). PLD thin films were grown on silicon substrates at 500°C from the ablation of a 8YSZ ceramic target by a KrF excimer laser. RMS thin films were obtained by direct current magnetron sputtering of a Zr/Y metallic target in an oxygen/argon atmosphere. The deposition rate of the PLD technique using an UV excimer laser delivering pulses at a repetition rate of 40Hz was found two orders of magnitude lower than the RMS method one. Both techniques led to the growth of crystalline films with a (111) preferential orientation. PLD films were dense and featureless whereas RMS ones exhibited well defined but compact columnar structure. Growth of a YSZ film of about 1μm covering a rough and porous commercial anode support (NiO–YSZ cermet) was successfully carried out with both methods.

Structural and discharging properties of MgO thin films prepared by pulsed laser deposition

In this work, pulsed laser-deposited thin films of MgO were studied for application in plasma display panels. The firing voltage (FV) of discharge cells with MgO films was measured and the film structure was investigated as a function of film deposition conditions. MgO thin films were deposited at oxygen pressure and substrate temperature between 0.02–5 Pa and 260–600 °C, respectively. The structure of thin films was investigated by using X-ray diffraction, X-ray reflection and atomic force microscopy methods. It was found that the FV is strongly correlated with the film deposition conditions and structural properties. In general, the FV values were smaller for the films with higher crystallinity and density. The crystallinity and the density of the films increased when the deposition temperature was raised and the O 2 pressure was reduced. The lowest FV values (~ 120 V) were obtained at the growth temperature of 550 °C and at O 2 pressures below 1 Pa.

Cathodoluminescence degradation of PLD thin films

The cathodoluminescence (CL) intensities of Y2SiO5:Ce3+, Gd2O2S:Tb3+ and SrAl2O4:Eu2+,Dy3+ phosphor thin films that were grown by pulsed laser deposition (PLD) were investigated for possible application in low voltage field emission displays (FEDs) and other infrastructure applications. Several process parameters (background gas, laser fluence, base pressure, substrate temperature, etc.) were changed during the deposition of the thin films. Atomic force microscopy (AFM) was used to determine the surface roughness and particle size of the different films. The layers consist of agglomerated nanoparticle structures. Samples with good light emission were selected for the electron degradation studies. Auger electron spectroscopy (AES) and CL spectroscopy were used to monitor changes in the surface chemical composition and luminous efficiency of the thin films. AES and CL spectroscopy were done with 2 keV energy electrons. Measurements were done at 1×10−6 Torr oxygen pressure. The formation of different oxide layers during electron bombardment was confirmed with X-ray photoelectron spectroscopy (XPS). New non-luminescent layers that formed during electron bombardment were responsible for the degradation in light intensity. The adventitious C was removed from the surface in all three cases as volatile gas species, which is consistent with the electron stimulated surface chemical reaction (ESSCR) model. For Y2SiO5:Ce3+ a luminescent SiO2 layer formed during the electron bombardment. Gd2O3 and SrO thin films formed on the surfaces of Gd2O2S:Tb3+ and SrAl2O4:Eu2+,Dy3+, respectively, due to ESSCRs.

Study of Luminescence from GaN : Tb3 + Powders and Thin Films Deposited by MOVPE and PLD Methods

Due to the recent commercial interest in nitride-based optoelectronics and rare-earth emission in nitride materials, the structural and optical characteristics of powders and thin films have been investigated in this work. The powder samples were made using a three-step solution method. Pulsed laser deposition (PLD) and metallorganic vapor phase epitaxy (MOVPE) methods were utilized for depositing films on sapphire substrates. The GaN powders with activator concentrations up to 8 atom % exhibited luminescence due to the transitions under cathodoluminescence (CL) as well as under photon excitation. Both near-band-edge emission and activator emission have been observed in PLD thin films made from the corresponding powders. X-ray diffraction revealed polycrystalline PLD thin films with a preferred growth direction along the axis, while scanning electron micrographs showed rough film morphology with submicrometer particles. CL emission from accompanied by near-band-edge emission and defect emissions from the GaN host was observed for the MOVPE films made using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)terbium but not films made with tris(isopropylcyclopentadienyl)terbium. Despite visible luminescence from in GaN powders and thin films, no energy transfer from the host to activator ions was observed. This suggests that is unlikely to fluoresce if used in a GaN-based optoelectronic device.