Growth and oxidization stability of cubic
Zr1-xGdxN solid solution thin films
Carina Höglund, Björn Alling, Jens Jensen, Lars Hultman, Jens Birch and R. Hall-Wilton
Linköping University Post Print
N.B.: When citing this work, cite the original article.
Original Publication:
Carina Höglund, Björn Alling, Jens Jensen, Lars Hultman, Jens Birch and R. Hall-Wilton,
Growth and oxidization stability of cubic Zr1-xGdxN solid solution thin films, 2015, Journal
of Applied Physics, (117), 19, 195301.
http://dx.doi.org/10.1063/1.4921167
Copyright: American Institute of Physics (AIP)
http://www.aip.org/
Postprint available at: Linköping University Electronic Press
Growth and oxidization stability of cubic Zr1−xGdxN solid solution thin films
C. Höglund, B. Alling, J. Jensen, L. Hultman, J. Birch, and R. Hall-Wilton
Citation: Journal of Applied Physics 117, 195301 (2015); doi: 10.1063/1.4921167
View online: http://dx.doi.org/10.1063/1.4921167
View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/117/19?ver=pdfcov Published by the AIP Publishing
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Growth and oxidization stability of cubic Zr
12xGd
xN solid solution thin films
C.H€oglund,1,2,a)B.Alling,2,3J.Jensen,2L.Hultman,2J.Birch,2and R.Hall-Wilton1,4
1
European Spallation Source ESS AB, P.O. Box 176, SE-221 00 Lund, Sweden 2
Department of Physics, Chemistry and Biology (IFM), Thin Film Physics Division, Link€oping University, SE-581 83 Link€oping, Sweden
3
Max-Planck-Institut f€ur Eisenforschung GmbH, D-402 37 D€usseldorf, Germany 4
Mid-Sweden University, SE-851 70 Sundsvall, Sweden
(Received 27 March 2015; accepted 28 April 2015; published online 15 May 2015)
We report Zr1xGdxN thin films deposited by magnetron sputter deposition. We show a solid
solubility of the highly neutron absorbing GdN into ZrN along the whole compositional range, which is in excellent agreement with our recent predictions by first-principles calculations. An oxi-dization study in air shows that Zr1xGdxN with x reaching from 1 to close to 0 fully oxidizes, but
that the oxidization is slowed down by an increased amount of ZrN or stopped by applying a cap-ping layer of ZrN. The crystalline quality of Zr0.5Gd0.5N films increases with substrate
tempera-tures increasing from 100C to 900C. VC 2015 Author(s). All article content, except where
otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4921167]
INTRODUCTION
Gadolinium compounds and their alloys are of interest due to the high thermal neutron absorption cross-section of Gd and due to its magnetic properties. Among all naturally occurring elements, Gd has the highest thermal neutron absorption cross-section of 49 700 b. One of its stable iso-topes, 157Gd, with a natural abundance of 15.65% has an absorption cross-section as high as 259 000 b and is commer-cially available. Gd is ferromagnetic at temperatures below 289 K, which makes it a common element in ferromagnetic superconductors. At higher temperature it is strongly para-magnetic, resulting in Gd(III) chelates being the leading con-trast agents in magnetic resonance imaging.1
The high probability of Gd to absorb thermal neutrons enables new types of neutron detectors that could raise detec-tor resolution and detection efficiency to a completely new level. A second application is found within thermal neutron shielding, where the nowadays very large and heavy materi-als could be replaced by micro-engineered and miniaturized solutions.2New large-scale neutron scattering facilities like the European Spallation Source (ESS)3and target station 2 at the Spallation Neutron Source (SNS)4are striving to push the limits within these fields with requirements that are not yet fulfilled by state of the art technologies. In addition to the enhanced requirements there is a severe shortage in the supply of 3He gas,5,6 the nowadays primarily used neutron absorbing and converting material in neutron detectors. This has forced the community to search for alternative solu-tions7,8and the boron isotope10B is seen as one of the most promising replacements.9–15The main options are technolo-gies based on10B4C thin films and this is a field in which the
authors’16–18and Nowak and co-workers’19research and de-velopment work have enabled rapid progress. These types of detectors are mainly intended for use in large area gaseous
neutron detectors and a significant fraction of the detectors at the ESS will be based on this technology.20,21A limitation of the 10B4C technology is the relatively low efficiency of a
few percent for one layer of 10B4C to absorb and convert a
neutron into the two reaction particles7Li and4He (10Bþ n ! 7Liþ4Heþ c) and to detect those.22,23The solution has
been to collect the neutrons over several layers,9,24–27 result-ing in the detector mechanics beresult-ing the limitresult-ing factor for the spatial resolution. Instead, a detector containing only one, several micrometer thick, layer of Gd could provide an efficiency of approximately 20%, or around 50% if the iso-tope155Gd or157Gd is used.28,29Such a detector would fulfill the efficiency and resolution requirements of 20% and <0.2 mm, respectively, and allow for parallax corrections in the varying sample-detector distance setup in the Neutron Macromolecular Crystallography (NMX) instrument that will be built at the ESS.3Initial studies on the potential of solid neutron converters in combination with micro pattern gaseous detectors have been reported.30 Schulz and co-workers developed micro-strip gas chambers (MSGC)31 that contain neutron converting layers of Gd29,32and in par-allel Sauli developed gas electron multiplication (GEM) neu-tron detectors, which can be an alternative to MSGCs.33 Both technologies have the potential to be used in an instru-ment like NMX, but require long-term stable thin films con-taining high amounts of Gd. GdN, which has a higher Gd content per unit volume than Gd2O334or even pure Gd could
be a suitable solution.
The reduction of experimental backgrounds for neutron spallation sources is a very topical issue35 and instrument performance is typically defined by signal-to-background ratios. While the signal is defined by the intensity of the source, the background can be improved with more advanced instrument designs, resulting in improved performances. Additionally, large volumes of radiation shielding are required and, therefore, significant cost savings are expected for advances in the search for new effective materials.2,36
a)Email: carina.hoglund@esss.se. Tel.:
þ46 72 179 2023.
0021-8979/2015/117(19)/195301/6 117, 195301-1 VCAuthor(s) 2015
Whilst the work this far has concentrated on reducing fast neutron and gamma ray background, there is also an effort needed in reducing the background from thermal neutrons preventing “cross-talk” between local neutron detector ele-ments. Using Gd compounds, neutron shielding can be engi-neered to be both compact and very efficient. At the moment, this is typically solved by using Gd in the form of Gd2O3that is mixed with an epoxy and painted onto surfaces
to be shielded, but epoxy is not ideal due to outgassing and does not allow for something mechanically precise. Therefore, stable Gd-rich compounds that are precisely de-posited as thin films present a potential application niche.
During the past ten years, it has been shown that rocksalt-structured GdN thin films can be grown both with physical vapor deposition techniques like reactive sputter-ing,37–40 reactive thermal evaporation,41–43 and molecular beam epitaxy,44,45 but also with metal-organic chemical vapor deposition processes.46,47 The intention has mainly been to deposit high quality films for investigations of their optical and magnetic properties. The foremost issue related to growth has been the high tendency to oxidization, which (when needed) has been solved with buffer and/or capping layers.37,43,44,48 GdN single crystals have been shown to have a metallic electrical conductivity.49For use in a neutron detector, we are seeking a solution for a stable enough com-pound that is electrically conducting and contains high amounts of Gd. The stable oxide Gd2O3, therefore, has the
drawback that it is an insulator, which hinders the transport of built up charges in a detector, and that the atomic concen-tration of Gd is only 40% of the compound, which lowers the neutron absorption efficiency significantly.
Recently, the authors presented a first-principles study on the mixing thermodynamics of GdN with the transition metal nitrides TiN, ZrN, and HfN.50These binary compounds were chosen because they are thoroughly studied, chemically quite inert, thermally stable, and electrically conducting.51,52 They are also known to be good oxidization barriers and are industri-ally used as such.53 To alloy GdN with one of these com-pounds could result in a solid solution that is straightforward to deposit as a thin film, that is both conducting and oxidization resistant, and contains a high amount of Gd.
In this experimental study, we have chosen ZrN as the alloying compound to explore the solid solubility of ZrN and GdN and the resulting thin film properties. ZrN was pre-ferred over TiN because the mixing enthalpy calculations in Ref.50stipulates phase separation for the latter, while HfN was disregarded because it is more exotic, less explored, and considerably more expensive than ZrN. We have deposited solid solution films over the full compositional range of Zr1xGdxN from ZrN to GdN, thus verifying theoretical
pre-dictions of the mixing tendency of the alloy. Results for oxi-dization resistance and crystalline quality are also presented.
EXPERIMENTAL PROCEDURES Thin film deposition
Deposition experiments were performed in an ultrahigh vacuum chamber at a base pressure of 4 106Pa. Reactive magnetron sputter deposition using unbalanced type II
magnetrons with 75 mm diameter Zr and Gd elemental targets was used to grow Zr1xGdxN films, with x ranging from 0 to
1, onto polished Al2O3(0001) and Si(001) substrates. The Ar
and N2partial pressures were set to 0.53 and 0.13 Pa,
respec-tively. As references for samples included in the oxidization study and as diffusion barriers at high deposition tempera-tures, seed and/or capping layers of ZrN(111) or ZrN(001) were deposited additionally. The deposition system is described in detail elsewhere.54 The ZrN seed and capping layers were chosen because they are known to be temperature stable, efficient diffusion barriers,51,53 and serve as lattice-matched templates for epitaxial film growth, especially for the ones with the lowest GdN contents. Al2O3(0001) substrates
were chosen as the base substrates due to their temperature stability and to avoid overlap of film peaks with substrate peaks in X-ray diffraction (XRD).
Prior to deposition, the substrates were cleaned in ultra-sonic baths of trichloroethylene, acetone, and 2-propanol and blown dry in dry N2. The substrate heater was slowly ramped
up to the chosen deposition temperature, which was con-trolled by a thermocouple positioned behind the substrate and calibrated by pyrometry. For seed and capping layers, the same substrate temperatures were used as during the film depositions.
The Zr and Gd magnetron powers were set to a total power of 300 W, with relative adjustments of the powers to obtain various compositions, x between 0 and 1, in Zr1xGdxN. Rutherford Backscattering Spectrometry (RBS)
results show that for a molar fraction of x¼ 0.5, the Zr and Gd magnetron powers need to be 200 W and 100 W, respectively.
Thin film analysis techniques
Compositional analysis was mainly performed with RBS using a 2.0 MeV Heþbeam at 6 incidence and 172 scattering angle. The advantage with RBS for Zr1xGdxN
thin films is the possibility to obtain very accurate composi-tional ratios between the metal atoms. The sensitivity for contaminants such as H (Heþ can not be backscattered on H), C, and O is low. However, C and N can be distinguished if the films contain several atomic percent of each kind. For this study, RBS was used to determine the ratio between Zr and Gd, meaning x. It was also a key technique to judge whether the film was oxidized or not, since that can be extracted from the data both by looking at change in the areal density of the film when oxidized and/or by determining the amount of O relative to N.
As a complementary technique to determine the compo-sition of the light elements in the Zr1xGdxN thin films, we
have used time-of-flight Elastic Recoil Detection Analysis (ToF-ERDA). This compositional analysis technique was performed using a 31.5 MeV 127I8þ beam at 66 incidence and 45 recoil scattering angle. The recoil energy of each element was converted to relative elemental depth profiles using the CONTES code.55 As the sensitivity is good for light elements, we have used ToF-ERDA to quantify the amounts of N and impurities like Ar (from sputter gas), O, C, and H in the film.
The Gd isotope distribution in the films was measured by time-of-flight Secondary Ion Mass Spectrometry (ToF-SIMS) using a TOF.SIMS V instrument (ION-TOF GmbH, Germany). A dual-beam depth profiling procedure was applied with a 1.0 keV O2þsputter beam, having a current of
300 nA and scanned over 400 400 m2. A pulsed 30 keV Biþbeam was used as the analysis beam. The current was typically 1.5 pA with an analysis field of view of 100 100 lm2 at the centre of the sputter crater. Positive
ToF-SIMS spectra were acquired between the sputter cycles in the so-called spectroscopy mode (mass resolution m/Dm 8000, beam spot 5 lm).
The crystal structure was characterized by Cu Ka XRD using a Philips Bragg-Brentano diffractometer. The film thickness was measured with cross-sectional scanning elec-tron microscopy (SEM) for films with high ZrN content using a LEO 1550 instrument, equipped with an in-lens de-tector operated at 5 kV at a working distance of3 mm.
RESULTS AND DISCUSSION
The solid solubility of GdN into ZrN was explored by depositing a series of Zr1xGdxN films with 0 x 1 at a
substrate temperature of 700C. The films were sandwiched between seed and capping layers of ZrN to avoid any reac-tions with the substrate or oxidization due to exposure to air before the characterization was done. It has been shown pre-viously for the chemically similar Sc1xAlxN system that a
comparison between calculated lattice spacings over the whole composition range with experimental measurements is a reliable tool to reveal secondary phase formation during film growth.56–58 Applying this comparison to the present system, Figure1shows the calculated lattice parameters for the cubic disordered solid solutions of Zr1xGdxN from Ref. 50together with the experimental curve, which is a combina-tion of the relacombina-tions between the Zr and Gd metals obtained from RBS and the lattice parameters calculated from XRD data. The measured lattice parameters follow the same increasing trend with increasing GdN content as the calcula-tions. The calculated lattice parameters slightly overestimate our measured values, which is the usual condition found for calculations employing the generalized gradient approxima-tion for exchange-correlation effects in nitrides.57,59
However, this overestimation vanishes for the GdN rich compositions. In Ref. 50, it was shown that the theoretical overestimation for pure GdN with respect to experiments is smaller compared to the case of pure ZrN. One should also keep in mind that the calculations were done for the ideal nitrogen stoichiometry while a slight understoichiometry is found in our measurements (see below). The effect of such understoichiometry on the lattice spacing can be different in different nitrides, possibly adding to the slight differences in slope between theory and experimental curves in Figure 1. However, the gradual increase in lattice spacing with compo-sition almost follows Vegard’s rule60and the theoretical pre-dictions and therefore it is a strong evidence of the formation of solid solutions over the full compositional range.
To determine the most favorable substrate temperature for high quality epitaxial Zr1xGdxN films, Zr0.5Gd0.5N was
deposited with a ZrN seed and capping layer onto Al2O3(0001) at substrate temperatures between 100 and
900C. As seen in the different XRD scans in Figure2, it is mainly the orientation of the ZrN that determines the orienta-tion of the Zr0.5Gd0.5N. The preferred growth orientation for
the highest (900C) and lowest (100C) applied tempera-tures is h111i, while temperatures between 300 and 700C allow for a mixture of h111i and h001i oriented growth. No other growth orientations were seen in longer overview scans. While the hexagonal symmetry of the Al2O3(0001)
substrate surface will favorh111i oriented nucleation at high temperatures, the in-plane lattice mismatch of Al2O3(0001)
compared to ZrN(111) is as large as 19.4%, which reduces the possibility of forming continuous epitaxial layers, in par-ticular, at limited growth temperatures. On the other hand, Petrov and co-workers have previously shown that increased adatom mobility, as induced by increased substrate tempera-ture, generally promotes a h001i preferred growth orienta-tion.61 Thus, the mixture of ZrN h111i and h001i oriented growth at intermediate growth temperatures may be explained by a competition between the driving forces for h111i oriented epitaxy and for h001i oriented growth due to
FIG. 1. Measured (this work) and calculated (Ref.50) lattice parameters for the cubic rocksalt solid solution of Zr1xGdxN with 0 x 1.
FIG. 2. XRD data from (111) and (001) oriented Zr0.5Gd0.5N films on
Al2O3(0001) and (111) and (001) oriented ZrN seed and capping layers
grown at substrate temperatures between 100 and 900C.
increased adatom mobility. At the highest temperature though, the h111i oriented preferred growth indicates that the interaction with the substrate becomes the determining factor. An additional observation is the shift of the Zr0.5Gd0.5N 111 peak towards higher angles, meaning
smaller out-of-plane lattice parameter, with increasing tem-perature. This behavior is consistent with an increasing influ-ence by the substrate surface lattice as the temperature is increases, as evidenced by the trend towardsh111i oriented growth. Also a nitrogen under-stoichiometry, as is often observed for reactively grown transition metal nitrides, may have a similar influence on the lattice parameter evolution. While it is beyond the scope of this work to clarify the rea-son for this temperature effect, we note that the coefficients of thermal expansion (CTE) of most transition metal nitrides (e.g., CTEZrN¼ 7–9 106K1) and sapphire perpendicular
to the C-plane (CTEAl2O3¼ 7–10 106K1) are very
simi-lar and cannot explain the simi-large observed peak shifts. The XRD data for the intermediate growth temperature 500C, which exhibits the highest 002 peak intensity, exhibits an inconsistency in the Zr0.5Gd0.5N 002 peak shift
direction. We find this interesting, as it is an indication of a material with anisotropic mechanical and/or structural prop-erties, as might be for the case in Ref.50predicted ordered structure of ZrGdN2. Nevertheless, the formation of that
phase could not be found in any of the measured XRD scans or X-ray pole figures (not shown), even though the compositional ratios were correct and the in-plane lattice mismatch was expected to be only 3.9% according to the calculated lattice parameters in Ref.50. Instead, the substi-tutionally disordered Zr0.5Gd0.5N solid solution was
observed for all applied substrate temperatures. It was noted in Ref. 50 that the predicted critical ordering temperature, Tc¼ 1020 K (747C), is in the same range as where bulk
diffusion becomes extremely slow in nitrides.55 Since sev-eral of our samples were grown at lower temperatures, the absence of an ordered phase illustrates that surface diffusion alone, which is active at all the considered temperatures, is insufficient to create a long-range metal-site ordering in this nitride system.
ToF-ERDA depth profiles were recorded for films that, according to RBS, contain x¼ 0.30 in Zr1xGdxN, both with
and without ZrN capping layers. Both films show composi-tional levels of H, C, F, and Ar below the ToF-ERDA detec-tion limit of 0.03 at. %. The level of O is also close to the detection limit in the film that was covered with a capping layer, while the film without a capping layer shows higher O levels close to the surface. This indicates that the films do not contain any O before they are exposed to air and start to oxidize. It also shows that the sputtering targets are pure and the vacuum conditions good enough to provide films without contaminations. We further conclude that no Ar has been incorporated during the sputter deposition. The N content in the as-deposited films has been determined by combining ToF-ERDA and RBS results and is found to be in the region of 45–50 at. %.
A ToF-SIMS depth profile of a typical GdN film sand-wiched between seed and capping layer of ZrN was recorded and an important result for future neutron detector applications
is that the natural abundance of the five most common isotopes in Gd, 155Gd¼ 14.8%,156Gd¼ 20.6%,157Gd¼ 15.7%,158Gd
¼ 24.8%, and160Gd¼ 21.8% could be confirmed.
To follow the oxidization of pure GdN without capping layer, 400 nm of GdN was deposited onto an Al2O3
sub-strate and then exposed to air at room temperature. The oxi-dation was followed by the surface color change, recorded every 4 s with a digital camera. The continuous oxidation process is illustrated by a selection of these images of GdN films on transparent Al2O3, exposed to air up to 19 h as
shown in Figure 3. The as-deposited sample had a silver-metallic color that within the first minutes changed to be more golden and then brownish. The rapid color change indi-cates that the oxidization starts immediately. After the brown appearance and within the first hour, all the colors of the rainbow brightly appeared after each other. During the fol-lowing few hours, the film appeared to be purple and green with some interference color gradients indicating a slight thickness gradient of the oxide and remaining film. After less than 19 h, the film has become fully transparent and is com-pletely oxidized. RBS measurements on a comcom-pletely oxi-dized film show that the majority of N has been replaced by O. A similar but much faster color change, probably due to a GdN film thicknesses of only100 nm, has been reported in Ref.41.
To investigate the oxidization stability of Zr1xGdxN, a
series of films with 0 x 1 were deposited with and with-out ZrN capping layers onto Si and Al2O3 substrates at
400C. These films were measured with RBS within two weeks after they were deposited. A second measurement was done 3–4 months after deposition, for those films that were not fully oxidized already in the first measurement. All sam-ples were stored in room temperature and in air. The results are presented in Figure 4 and show that films with a high amount of GdN oxidize within a very short time. Increasing the amount of ZrN significantly slows down the oxidization and films with x 0.3 were just slightly oxidized even after several months. The idea to alloy GdN with a chemically more stable transition metal nitride with the purpose to pre-vent it from oxidization is thus working, although oxidation can not fully be avoided even with GdN contents as low as x¼ 0.2.
FIG. 3. Color change for a GdN thin film on Al2O3substrate during
expo-sure to air for up to 19 h.
Figure 5 shows typical RBS spectra of Zr1xGdxN,
recorded from the same film, both as-deposited and after 4 months. Here, we show Zr0.6Gd0.4N on Si. Comparing the Zr
and/or Gd spectra, respectively, clearly shows the increase in the areal density when O replaces N during oxidization. The complete transition is also seen in that the as-deposited film contains no oxygen (within the detection limit) and the oxi-dized film contains no nitrogen. The ToF-ERDA depth profile of the as-deposited film, mentioned above, confirmed that those films were free from oxygen. Even though the nitrogen completely escapes from the film and is replaced by oxygen, the ratios between the Gd and Zr content stay constant for all measured samples before and after oxidization, respectively.
For films that were oxidized half way through in the oxi-dation study in Figure4, an abrupt interface between the oxi-dized layer on top and the not oxioxi-dized layer below can be identified in the analyses of the RBS-spectra and their corre-sponding simulations. We therefore conclude that within the 2 mm 2 mm RBS beam spot, the thickness of the formed oxide is the same within the measurement errors. We find it an interesting observation that none of all the samples in the oxidization study showed a gradient at the interface between the oxidized layer and the intact nitride layer, but always a sharp transition. This is in agreement with the observations
from the surface color change in Figure3, where a uniform interference color over the whole film surface, 8 mm 10 mm, within the first 30 min corresponds to a uniformly thick oxide layer in the film.
For several applications, including highly efficient neu-tron detectors, it is possibly more beneficial to protect a film that contains a high amount of Gd with a thin (preferably conducting) oxidization barrier, than to use a Gd compound that degrades over time. We therefore tested a 260 nm Zr0.5Gd0.5N film deposited with both 35 nm ZrN capping and
seed layers. The film was measured with RBS soon after it was deposited and again after storing it in air and at room temperature for one year. Within the measurement accuracy, the compositions of the Zr0.5Gd0.5N film and ZrN protective
layers were not changed during that time. This experiment shows that applying a capping and seed layer prevents the film from oxidizing when it is exposed to air and promises a long lifetime of the nitride structure, even with higher amounts of GdN. The minimum required thickness of the protective layers remains to be determined for the different compositions. The final decision, whether to use capping layers or films with lower Gd-content for neutron detector applications depends on the detector requirements and if the films can be kept in oxygen free atmosphere.
It was also observed by RBS analysis that the inter-face between a Zr0.55Gd0.45N film and a Si substrate after
one year still exhibited an abrupt transition, when only a ZrN capping layer but no seed layer was used. This shows that no significant amount of substrate elements have dif-fused into the film, even though there is a native oxide on the Si substrate, but rather that gaseous oxygen is responsi-ble for the oxidation. The same observation was made for all measurements included in Figure 4 that showed partly oxidized films, where the oxygen only was found in the top layers.
CONCLUSIONS
We have shown that (001) and (111)-oriented solid solution Zr1xGdxN alloy thin films can be grown by
magnetron sputter deposition over the whole composi-tional range from ZrN to GdN, in excellent agreement with theoretical predictions. The alloys were substitution-ally disordered and no ordered alloys could be observed for deposition temperatures up to 900C. The oxidization of the Zr1xGdxN films is substantially reduced when
increasing the amount of ZrN and can even be arrested by applying a capping layer of ZrN. Even though this study is an initial experimental work on Gd containing compounds with applications within neutron detection and shielding in mind, it adds a significant amount of infor-mation to the judgment about the potential of these mate-rials for those applications.
ACKNOWLEDGMENTS
The authors would like to acknowledge the Tandem Laboratory at Uppsala University for giving access to their ion beam facilities, and Dr. Muhammad Junaid for his laboratory assistance. B.A. acknowledges the financial
FIG. 4. Level of oxidization in Zr1xGdxN (0 x 1) thin films from RBS,
obtained within 2 weeks or 3–4 months after deposition.
FIG. 5. Measured data from RBS of an as-deposited and later fully oxidized Zr0.6Gd0.4N thin film, together with simulated elemental spectra for Gd, Zr,
N (as-deposited state only), and O (oxidized state only), respectively.
support from the Swedish Research Council (VR) through Grant Nos. 621-2011-4417 and 330-2014-6336.
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