Reflection High-energy Electron Diffraction Measurements Research Articles

In segregation influence on properties of InAs quantum dots in dots-in-a-well

We investigated the growth of InAs quantum dots (QDs) in a dots-in-a-well (DWELL) from the perspective of the influence of In segregation from the InGaAs layers in the DWELL. Reflection high-energy electron diffraction (RHEED) measurements during the growth of the lower InGaAs layer indicated that In segregation increased with the In composition of the InGaAs layer. The estimated In segregation values were consistent with the decreases in the critical thickness for the QDs growth and the total volume variations of the grown QDs. These results illustrate that the segregated In from the lower InGaAs layer contributes to the QD growth in the DWELL, and their density increases. Furthermore, RHEED measurements during the growth of the upper InGaAs layer indicated the suppression of the deformation of embedded QDs , which could partially contribute to the longer emission wavelength of the QDs in the DWELL.

Surface chemical states and structures of epitaxial Mg2Sn thermoelectric thin films

Abstract Evaluation of the surface chemical states and structures of thermoelectric thin films is vital for the successful fabrication and operation of microscale thermoelectric devices incorporating such films. The chemical states and structures present in the surface layers of epitaxially grown Mg2Sn thermoelectric thin films were evaluated by Auger electron spectroscopy and reflection high-energy electron diffraction measurements. An oxide layer about 5 Å thick was shown to form on the surface of epitaxially grown Mg2Sn thermoelectric thin films on exposure to air, giving meaningful insights into potential ways of improving the microfabrication of thin-film-based miniaturized thermoelectric devices.

Metallic band structure of CaF2 thin films grown on silicon(1 1 1): Possible formation of CaSi2

We grew epitaxial 10 monolayer (ML) CaF2 films on a Si(111) substrate and measured its electronic structure with angle-resolved photoemission spectroscopy. Reflection high-energy electron diffraction measurements showed the 1×1 streaks of the grown film with no sign of the formation of the Ca-Si surface superstructure at the growth temperature of 400–500 °C. The band dispersion of the films was metallic in contrast to the highly insulating nature of bulk CaF2. The metallic band dispersion did not change with additional Si deposition (1–10 ML) on the CaF2 film. We suggest that CaSi2 may be formed near the surface layers and this shows that the CaF2/Si is not an ideal insulator/semiconductor heterostructure for application in atomically thin electronic devices.

Growth of 3C-SiC(111) on AlN/off-axis Si(110) hetero-structure and formation of epitaxial graphene thereon

A cubic silicon carbide (3C-SiC) film was fabricated by pulsed laser deposition on an aluminum nitride layer grown on an off-axis Si(110) substrate. This is the first report about the use of off-axis Si(110) substrates for manufacturing SiC/AlN/Si multilayers. A high-quality epitaxial 3C-SiC(111) film without rotation domains or twins, as evidenced by reflection high-energy electron diffraction (RHEED) measurements, was successfully obtained by using a wurtzite AlN(0001)/off-axis Si(110) substrate. On this 3C-SiC film, graphene was formed through annealing in ultrahigh vacuum at 1200 °C and its structure and chemical bonding were investigated via in situ RHEED and X-ray photoelectron spectroscopy; the full width at half maximum of the C 1s core level peak and the root-mean-square surface roughness were 0.60 eV and 0.14 nm, respectively, which were substantially lower than those (0.73 eV and 1.44 nm) previously reported for a graphene sample with similar thickness but formed on a SiC/AlN/on-axis Si(110) substrate.

Reflection high energy electron diffraction (RHEED) study of ice nucleation and growth on Ni(111): influences of adspecies and electron irradiation.

How interfacial molecular interactions influence nucleation and growth processes of water ice is explored using pristine, oxygenated, and CO-adsorbed Ni(111) substrates based on RHEED, together with the effects of high-energy electron irradiation on the crystallization kinetics. A monolayer of amorphous solid water deposited onto the pristine Ni(111) substrate crystallizes into ice Ic at ca. 150 K, whereas ice Ih (Ic) is formed preferentially during water vapor deposition at 135 K (125 K). The ice nucleation tends to be hampered on the oxygenated Ni(111) surface because of the hydrogen bond formation with chemisorbed oxygen, leading to the growth of randomly-oriented ice Ic crystallites via spontaneous nucleation. The amorphization and recrystallization of initially crystalline ices are observed during prolonged RHEED measurements at 20 and 70 K, respectively, signifying that high-energy electron irradiation has both thermal and non-thermal effects on the water phase transition. The epitaxial growth (non-epitaxial growth) of ice occurs during electron irradiation of amorphous solid water formed on the pristine and oxygenated Ni(111) substrates (CO-adsorbed Ni(111) substrate) even at 100 K (120 K) because nucleation and growth are initiated at the substrate interface (in the ASW film interior).

Structure and magnetic properties of an epitaxial Fe(110)/MgO(111)/GaN(0001) heterostructure

We present the structural and magnetic properties of fully epitaxial Fe(110)/MgO(111)/GaN(0001) tunnel barrier structures grown by molecular beam epitaxy. In-situ reflection high-energy electron diffraction and ex-situ X-ray diffraction measurements indicate epitaxial Fe(110) films on top of an epitaxial 2 nm MgO(111) tunnel barrier on GaN(0001). X-ray reflectivity measurements confirm a roughness of approximately 0.3 nm and 0.7 nm for the MgO/GaN and the Fe/MgO interfaces, respectively. Results of in-situ magneto-optical Kerr effect measurements indicate that 1 nm thick Fe film shows signs of in-plane ferromagnetism at room temperature. Vibrating sample magnetometer measurements determine the saturation magnetisation of the 5 nm thick film to be 1660 ± 100 emu/cm3 and show that this system has a predominant uniaxial anisotropy contribution despite the presence of cyclic twinned crystals. We estimate the values of effective uniaxial (KUeff) and cubic (K1eff) anisotropy constants to be 11700 ± 170 erg cm−3 and −3300 ± 700 erg cm−3 by fitting the angular dependence of the magnetising energy.

Van der Waals epitaxy of SnS film on single crystal graphene buffer layer on amorphous SiO2/Si

Conventional hetero-epitaxial films are typically grown on lattice and symmetry matched single crystal substrates. We demonstrated the epitaxial growth of orthorhombic SnS film (∼500 nm thick) on single crystal, monolayer graphene that was transferred on the amorphous SiO2/Si substrate. Using X-ray pole figure analysis we examined the structure, quality and epitaxy relationship of the SnS film grown on the single crystal graphene and compared it with the SnS film grown on commercial polycrystalline graphene. We showed that the SnS films grown on both single crystal and polycrystalline graphene have two sets of orientation domains. However, the crystallinity and grain size of the SnS film improve when grown on the single crystal graphene. Reflection high-energy electron diffraction measurements show that the near surface texture has more phases as compared with that of the entire film. The surface texture of a film will influence the growth and quality of film grown on top of it as well as the interface formed. Our result offers an alternative approach to grow a hetero-epitaxial film on an amorphous substrate through a single crystal graphene buffer layer. This strategy of growing high quality epitaxial thin film has potential applications in optoelectronics.

Epitaxial growth of superconducting MgB2 thin films with a Mg buffer layer at 110 °C

Since the discovery of MgB2, its application to superconducting electronics has been limited by the absent of proper microfabrication techniques. In this study, we grew crystalline MgB2 thin films using molecular beam epitaxy at a low substrate temperature of 110 °C under ultra-high vacuum of about 10−6 Pa. MgB2 thin films were deposited with an epitaxial Mg buffer layer on c-plane 4H-SiC or sapphire substrates. In spite of the low growth temperature, superior crystallinity and surface flatness were confirmed by in situ reflection high-energy electron diffraction and X-ray diffraction measurements. Moreover, we successfully confirmed the occurrence of a sharp superconducting transition at 27 K.The present growth temperature was lower than any in prior reports on superconducting MgB2 thin films, and is lower than the applicable temperature of an organic-based lift-off resist. Our new MgB2 thin film growth process is promising for the development of an alternative nanofabrication technique for MgB2 thin films by means of a standard lift-off process with an organic resist.

Reflection high-energy electron diffraction measurements of reciprocal space structure of 2D materials

Knowledge on the symmetry and perfection of a 2D material deposited or transferred to a surface is very important and valuable. We demonstrate a method to map the reciprocal space structure of 2D materials using reflection high energy diffraction (RHEED). RHEED from a 2D material gives rise to ‘streaks’ patterns. It is shown that from these streaks patterns at different azimuthal rotation angles that the reciprocal space intensity distribution can be constructed as a function of momentum transfer parallel to the surface. To illustrate the principle, we experimentally constructed the reciprocal space structure of a commercial graphene/SiO2/Si sample in which the graphene layer was transferred to the SiO2/Si substrate after it was deposited on a Cu foil by chemical vapor deposition. The result reveals a 12-fold symmetry of the graphene layer which is a result of two dominant orientation domains with 30° rotation relative to each other. We show that the graphene can serve as a template to grow other materials such as a SnS film that follows the symmetry of graphene.

Room-temperature laser annealing for solid-phase epitaxial crystallization of β-Ga2O3 thin films

The epitaxial crystallization of β-Ga2O3 thin films on NiO-buffered α-Al2O3(0001) substrates via the solid-phase crystallization of amorphous Ga2O3 thin films by KrF excimer laser annealing at room temperature (RT) was examined. The results of X-ray and reflection high-energy electron diffraction measurements indicated that the epitaxial β-Ga2O3 thin films were fabricated by RT laser annealing. The optical bandgap of the thin films was estimated to be 4.9 eV from the results of UV/vis transmittance measurements. In the cathodoluminescence spectrum, UV–green luminescence was observed for the thin films. These optical properties are similar to those of bulk β-Ga2O3.

Stoichiometry as key to ferroelectricity in compressively strained SrTiO3 films

While strain is a powerful tuning parameter for inducing ferroelectricity in thin film oxides, the role of stoichiometry control is critical, but far less explored. A series of compressively strained SrTiO3 films on (001) (LaAlO3)0.3(Sr2AlTaO6)0.35 substrates were grown by hybrid molecular beam epitaxy where the Ti cation was supplied using a metal-organic titanium tetraisopropoxide molecule that helps systematically and precisely control Sr:Ti stoichiometry in the resulting films. A stoichiometric growth window is located through X-ray diffraction and in-situ reflection high-energy electron diffraction measurements, which show a minimum out-of-plane lattice parameter as well as constant growth rate within the stoichiometric growth window range. Using temperature dependent optical second harmonic generation (SHG) characterization, a ferroelectric-to-paraelectric transition at T ∼ 180 K is observed for a stoichiometric SrTiO3 film, as well as a higher temperature structural transition at T ∼ 385 K. Using SHG polarimetry modeling, the polar point group symmetry is determined to be tetragonal 4mm with the polarization pointing out-of-plane of the film. The SHG coefficients, d31/d15=3 and d33/d15=21, were determined at 298 K. The ferroelectric transition disappears in films grown outside the growth window, thus proving the critical role of stoichiometry control in realizing strain-induced ferroelectricity.

Ambient temperature epitaxial growth of MgB2 thin films with a Mg buffer layer

We grew crystalline MgB2 thin films using molecular beam epitaxy at a low substrate temperature of 110 °C under an ultrahigh vacuum of about 10−6 Pa. MgB2 thin films were deposited on the (001) surface of a 4H-SiC substrate with an epitaxial Mg buffer layer. Superior crystallinity and surface flatness were confirmed by in situ reflection high-energy electron diffraction and X-ray diffraction measurements. The growth temperature was lower than any in prior reports on superconducting MgB2 thin films. Moreover, we successfully confirmed the occurrence of a sharp superconducting transition at 27.2 K.

Room-temperature fabrication of highly oriented β-Ga2O3 thin films by excimer laser annealing

Highly oriented crystalline Ga2O3 thin films were fabricated at room temperature (RT) by excimer laser annealing. Amorphous Ga2O3 thin films were grown on α-Al2O3 (0001) substrates at RT by the pulsed laser deposition method using a focused KrF excimer laser and a sintered β-Ga2O3 target. Amorphous precursor films were irradiated by a non-focused KrF excimer laser (100–250mJ/cm2) at RT. The results of x-ray and reflection high-energy electron diffraction measurements indicated that highly (101)-oriented crystalline β-Ga2O3 thin films were obtained after RT laser annealing. The optical bandgaps of the crystalline thin films were approximately 4.7–4.9eV, as determined from the UV/Vis transmittance. The film surfaces after laser annealing revealed slight planar grain growth, indicating a high degree of crystallinity and showed the root mean square roughnesses of 0.28–0.48nm.

Magnetically disordered phase in epitaxial iron-deficientFe3O4thin films

We report on the transport and magnetic properties of iron-deficient $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}\phantom{\rule{0.28em}{0ex}}(\mathrm{F}{\mathrm{e}}_{3\ensuremath{-}\ensuremath{\delta}}{\mathrm{O}}_{4})$ thin films grown with pulsed-laser deposition, where the stoichiometry and amount of cation vacancies are precisely controlled through changes in the oxygen partial pressure during growth. As the stoichiometry evolves from $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}$ to $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{3}$, three distinct structural and magnetic regimes emerge: a $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}$-like regime, a $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{3}$-like regime, and a transition regime. While reflection high-energy electron diffraction measurements reveal that films in all three regimes grow epitaxially cube-on-cube on MgO substrates, the transition-regime films are characterized by an absence of long-range, out-of-plane ordering in the film. Selected area electron diffraction measurements reveal the transition-regime films are well ordered on a local level, but not throughout the entire film. The structural disorder of the transition-regime films does not manifest itself in the transport properties, where a systematic change in resistivity, due primarily to variations in the $\mathrm{F}{\mathrm{e}}^{2+}:\mathrm{F}{\mathrm{e}}^{3+}$ cation ratio, occurs continuously throughout all three regimes. Large differences are observed, however, in the magnetic properties of the transition-regime films, which are reminiscent of magnetically disordered systems. We attribute this unique magnetically disordered state to magnetic frustration arising at the boundaries between the different locally ordered regions.

Invited: Electrochemical Properties for UHV-Prepared Pt/M Well-Defined Single Crystal Surfaces

Background Discussion on oxygen reduction reaction (ORR) mechanisms1) of alloy catalysts is complicated because of uncertainties in outermost surface structures. To clarify the effect of catalyst’s outermost surface structures on ORR, Markovic and co-workers2) evaluated ORR activities single-crystal planes of Pt3Ni. Their pioneering work clearly demonstrates that design of atomic arrangements of the catalyst surfaces directly links to developments in superior PEFC cathode electrode catalysts. To date, EC properties for the Pt-based single crystal alloy surfaces have been reported3-9): our approach is well-defined model-catalyst fabrications by using molecular beam epitaxy in ultra-high vacuum (UHV:~10-8Pa) condition. In this study, ORR activities and structural stabilities for the UHV-prepared well-defined Pt-based bimetallic (Pt/M) surfaces are discussed. Experimental The MBE apparatus and UHV-EC sample transfer system have been described earlier10). Pt-shell layers were prepared on fcc single crystal substrates through electron-beam vacuum depositions of another elements and thermal annealing in UHV. The resulting surface structures were verified with reflection high-energy electron diffraction (RHEED), IR reflection absorption (IRRAS) spectra for carbon monoxide (CO) adsorption, and scanning tunneling microsope (STM). The UHV-prepared samples were transferred to a N2-purged glove box without air exposure. CV curves are recorded in N2-purged 0.1 M HClO4. After that, LSV measurements were conducted in O2-saturated 0.1 M HClO4: RHE is used as a reference electrode. Results and discussion Pt/Au(111): On the basis of RHEED and CO-IRRAS measurements, epitaxial growth of Pt on Au(111) was confirmed. On the basis of the hydrogen-adsorption charges (QHad), we deduce that the 0.3nm-thick Pt almost covers the Au(111) substrate. The half-wave potential for the Pt0.3nm/Au(111) was ca. 10mV more positive than that of the Pt(111). In contrast, the potential for the Pt0.15nm/Au(111) shifted 60mV negatively. The results show that extended Pt(111) domains might correlate with the ORR activity enhancement. Ni/Pt(111)-skin: A UHV-STM image of the sample fabricated through 1ML-thick Ni deposition on ca. 800K-Pt(111) (Ni/Pt(111)-skin) showed 6-fold symmetric, honeycomb atomic arrangement. However, atomic-scale disorder with a corrugation of 0.06-0.12nm height is present at the topmost surface. XPS analysis showed positive shift of Pt 4f band. The LSV curve of the Ni/Pt(111)-skin shifted 70mV positively, suggesting that remarkable ORR activity enhancement is originated from the strains- and electronic-changes of the topmost Pt(111) lattice. Pt/Pd(111): Atomically flat PtmML/Pd(111) surfaces were prepared through Pt depositions on Pd(111) at 673 K. The LSV curve for the Pt2ML/Pd(111) showed 20mV positive shift relative to clean Pt(111). To evaluate EC stability of the PtmML/Pd(111), potential cycles (0.6~1.0V) were applied in O2 saturated 0.1M HClO4. Although the Pt layers less than 2MLs showed decrease in activity with increasing cycles, the activity of the Pt4ML/Pd(111) remained nearly unchanged during the cycles. EC Stability: Changes in ORR activities for the Pt-shell layers (Pt/Au(111), Ni/Pt(111)-skin, Pt/Pd(111)) during the potential cycles are summarized in Fig. 1. The results suggest that the Pt-shell layers thicker than 3MLs stabilize the topmost Pt(111) lattice in PEFC conditions. Acknowledgement This work was supported by NEDO. References 1)T.Toda et al. JES, 146, 3750 (1999).2)V.R.Stamenkovic et al. Science 315, 493 (2007).3)H. E. Hoster et al. Chemphyschem. 11, 1518 (2010).4)J.Baricuatro and M. Soriaga, Electrocatal. 1, 42, (2010).5)A.Bergbreiter et al. Chemphyschem. 11, 1505 (2010).6)S.Axnanda, et al. Chemphyschem. 11, 1468 (2010).7)M.Wakisaka, et al. Electrochem.Commun. 13, 317 (2011).8)I. E. L. Stephens et al. JACS 133, 5485 (2011).9)T.Rurigaki et al. JEAC, 716, 58 (2014).10)T.Wadayama et al. Electrochem.Commun. 12, 1112(2010). T.Wadayama et al. JPCC 115, 18589 (2011). Y.Iijima. et al., JEAC, 685, 79 (2012). Y.Yamada et al. Surf. Sci. 607, 54 (2013). N.Todoroki et al., PCCP, 15, 17771 (2013).

Smoothness and cleanliness of the GaAs (100) surface after thermal desorption of the native oxide for the synthesis of high mobility structures using molecular beam epitaxy

To prepare a GaAs substrate for molecular beam epitaxial (MBE) growth, the nominal ∼3nm native oxide is typically thermally desorbed into vacuum. To test the completeness and quality of this desorption, we describe a technique, which combines MBE, thermal desorption, atomic force microscopy (AFM), reflection high-energy electron diffraction (RHEED), and secondary ion mass spectroscopy (SIMS), for detecting roughness and trace residues of contamination on (100) GaAs surfaces before MBE growth. At all desorption temperatures in the range 600–665°C, our RHEED measurements show that the native oxide is largely desorbed within 4min. However, the SIMS and AFM data indicate that a residue of carbon invariably remains on the GaAs (100) surface, and tenaciously resists all further attempts at its removal by thermal desorption. Since thermal desorption of the native oxide has long been the standard technique for preparing GaAs substrates for MBE growth, we suggest that MBE growth on GaAs has in general been accomplished by epitaxially growing through a partial monolayer of carbon. We believe this is the likely reason for the generally unsatisfactory quality of GaAs MBE growth after lithographic patterning on previously MBE grown structures. Our AFM data also indicate that extended native oxide desorption times or high desorption temperatures not only are ineffective at removal of the carbon residue, but are always accompanied by additional strong roughening effects on the GaAs surface morphology. Finally, we demonstrate that smoother starting surfaces for MBE growth correlate well with higher two-dimensional carrier mobilities in the resulting AlGaAs/GaAs heterostructures.

Chemical and Morphological Analysis of 4H-SiC Surface Processed by Plasma Assisted Polishing

A novel polishing technique combined with the irradiation of atmospheric pressure plasma known as plasma assisted polishing (PAP) is proposed for the finishing of difficult-to-machine materials. In this paper, we mainly focus on the case of 4H-SiC substrate. We used helium-based water vapour plasma to modify the mechanical and chemical properties of the SiC surface. The results of X-ray photoelectron spectroscopy (XPS) measurements indicate that the surface was efficiently oxidized after plasma irradiation, and the main product was silicon oxide. A small amount of silicon oxycarbide was also observed which was identified as the interface oxide. The result of a nanoindentation test revealed that the hardness of oxidized SiC surface decreased by one order of magnitude compared with the unprocessed surface. The decrease of hardness of modified surface enables us to flatten the surface without forming any scratches and subsurface damage by using soft abrasive compared with the base material. We used CeO2 as the abrasive material in PAP, the hardness of which was near to that of the oxidized surface. The microscopic interferometer images of the PAP processed surface showed us that scratches disappeared and surface roughnesses also decreased from 4.410 nm p-v, 0.621 nm rms to 1.889 nm p-v, 0.280 nm rms. From the atomic force microscopy (AFM) images, a step and terrace structure was observed on the surface after PAP, which means that an atomically flat surface was obtained. We conducted reflection high-energy electron diffraction (RHEED) measurement to evaluate the residual strain of the PAP processed surface. The results indicate that the lattice constants approached the ideal value, which meansthat the PAP technique did not introduce crystallographical subsurface damage.

Slow-Polishing Iodine-Based Etchant for CdTe and CdZnTe Single Crystals

We report on new etching solutions for treatment of CdTe and CdZnTe surfaces based on the iodine-emerging etchant composition KIO3–KI–citric acid (C6H8O7). CdTe samples with (111), (110), and (100) orientations, and also Cd1−xZnxTe (x = 0.04, 0.1) samples with (111), (110), (100), and (211) orientations were investigated. The dissolution rate was determined as a function of solution composition, etchant storage time, disc rotation speed, and temperature. It was established that this chemical dissolution is diffusion controlled. Study of the chemical composition and structure of (211)B Cd1−xZnxTe surfaces etched under different conditions was carried out. x-Ray photoelectron spectroscopy measurements showed that a stoichiometric surface was achieved after briefly heating the etched surface in a vacuum. Reflection high-energy electron diffraction measurements revealed a high-quality single-crystalline surface layer in samples etched with KIO3–KI–citric acid solutions as compared with those etched with a bromine–methanol treatment. The etching compositions were shown to be useful for controlled removal of semiconductor material, and also for chemical polishing of CdTe-based surfaces.

Buffer-layer enhanced crystal growth of BaB6 (1 0 0) thin films on MgO (1 0 0) substrates by laser molecular beam epitaxy

Crystalline BaB6 (100) thin films can be fabricated on MgO (100) substrates by inserting a 2–3nm-thick epitaxial SrB6 (100) buffer layer by pulsed laser deposition (PLD) in ultra-high vacuum (i.e., laser molecular beam epitaxy). Reflection high-energy electron diffraction and X-ray diffraction measurements indicated the heteroepitaxial structure of BaB6 (100)/SrB6 (100)/MgO (100) with the single domain of the epitaxial relationship. Conversely, BaB6 thin films without the buffer layer were not epitaxial instead they developed as polycrystalline films with a random in-plane configuration and some impurity phases. As a result, the buffer layer is considered to greatly affect the initial growth of epitaxial BaB6 thin films; therefore, in this study, buffering effects have been discussed. From the conventional four-probe measurement, it was observed that BaB6 epitaxial thin films exhibit n-type semiconducting behavior with a resistivity of 2.90×10−1Ωcm at room temperature.

Development of Crystal Al MKIDs by Molecular Beam Epitaxy

We report here the effect of film qualities in superconductors on the properties of Microwave Kinetic Inductance Detectors (MKIDs). The sensitivity of MKIDs between crystal aluminum films and amorphous aluminum films is compared. The good quality and crystallized aluminum films have been prepared by using molecular beam epitaxy. We have confirmed that epitaxial Al(111) films were grown on Si(111) substrates with X-ray diffraction and in-situ reflection high-energy electron diffraction measurements. The amorphous aluminum films on the Si(111) wafers have been deposited by electron beam evaporation. We have measured transmission losses of MKIDs, noise spectrum and relaxation time against optical pulses, changing MKIDs’ bath temperature from 0.11 K to 0.55 K in a dilution refrigerator. Despite of the improvement in normal resistivity, the quasiparticle decay time of both films are equivalent and 450 μs at 0.11 K. The electrical noise equivalent power of the both MKIDs are also comparable and around \(10^{-17}~\mbox{W}/\sqrt{\mbox{Hz}}\). Fabrication details and performance data of both films are presented.