We have studied the electronic properties of AlxGa1-xN/GaN heterostructures by using Shubnikov¡Vde Haas(SdH) measurement. Two SdH oscillations were detected on the samples of x=0.35 and 0.31, due to the population of the first two subbands with the energy separations of 128 and 109 meV, respectively. For the sample of x=0.25, two SdH oscillations beat each other, probably due to a finite zero-field spin splitting. The spin-splitting energy is equal to 9.0 meV. The samples also showed a persistent photoconductivity effect after illuminating by blue light-emitting diode. For the part of experiment , we installed a "Regulator" on low temperature and high magnetic field system, in order to control the temperature of sample from 0.3K to 10K accurately. For the convenience of SdH measurements at different tempertures.

The design, fabrication, and characterizations of the spin-polarized AlxGa1-xN/GaN HEMT structure have been achieved for spintronic application. By band calculation within linear combination of atomic orbitals and two-band k·p methods, the theoretical spin-splitting energy and minimum-spin-splitting surface of wurtzite structure have been investigated as a function of the Fermi wavevector with various strain-relaxations. Base on these results, the design of host material of the nonballistic spin-FET has also been proposed. By optimizing the Al composition and n2DEG, the Fermi surface of two-dimensional electron gas is supposed to reach the minimum-spin-splitting surface to produce resonant spin-lifetime. Because the high quality AlxGa1-xN/GaN HEMT structure is necessary for realizing the spin-FET, the influence of the growth conditions on the polarity and structure quality of the GaN epilayer have been studied on the sample grown by plasma-assisted molecular beam epitaxy. Ga-polar AlGaN/GaN heterostructures on c-Al2O3 has been realized by growing over the Al-rich AlN nucleation layer. And the reduction of interface roughness and threading dislocation scatterings of the electrons in two-dimensional electron gas has also been achieved by growing GaN epilayer under slightly Ga-rich condition. Furthermore, the effect of different types of threading dislocation on the electron mobility of the AlxGa1-xN/GaN HEMT structure has been investigated as well. At low temperature, the electron mobility of two-dimensional electron gas in AlGaN/GaN heterostructures is majorly scattered by the edge type dislocation rather than the screw type. The designs of proposed host material for spin-FETs have been realized through growing high quality spin-polarized AlxGa1-xN/GaN HEMT structures with various Al composition (x= 0.191 ¡V 0.397) grown on c-Al2O3 by metalorganic vapor phase epitaxy. The high mobility (10682 cm2/Vs at 0.4 K), flat interface (surface roughness < 0.5 nm), and high quality HEMT provide a good environment to study the spin-splitting energy. To investigate the spin-splitting energy as functions of the Fermi wavevector, the Shubnikov-de Haas measurements were performed. A large spin-splitting energy (10.76 meV) has been fabricated in Al0.390Ga0.61N/GaN HEMT structure with kf = 8.14 ¡Ñ 108 m-1 for the host material of the Datta-Das spin-FET. And for the first time, the minimum-spin-splitting surface has been experimentally generated in Al0.390Ga0.61N/GaN HEMT structure with kf = 8.33 ¡Ñ 108 m-1 for the host material of the nonballistic spin-FET.

Plasmonic waves in solid-state are caused by collective oscillation of mobile charges inside or at the surface of conductors. In particular, surface plasmonic waves propagating at the skin of metals have recently attracted interest, as they reduce the wavelength of electromagnetic waves coupled to them by up to ~10 times, allowing one to create miniaturized wave devices at optical frequencies. In contrast, plasmonic waves on two-dimensional (2D) conductors appear at much lower infrared and THz-GHz frequencies, near or in the electronics regime, and can achieve far stronger wavelength reduction factor reaching well above 100. In this thesis, we study the unique machinery of 2D plasmonic waves behind this ultra-subwavelength confinement and explore how it can be used to create various interesting devices. To this end, we first develop a physically intuitive theoretical formulation of 2D plasmonic waves, whose two main components---the Coulomb restoration force and inertia of the collectively oscillating charges---are combined into a transmission-line-like model. We then use this formulation to create various ultra-subwavelength 2D plasmonic devices. For the 2D conductor, we first choose GaAs/AlGaAs heterostructure---a 2D electron gas consisting of massive (m*>0) electrons---demonstrating plasmonic bandgap crystals, interferometers, and negatively refracting metamaterials. We then examine a 2D plasmonic device based on graphene, a 2D electron gas consisting of effectively massless (m*=0) electrons. We theoretically show and experimentally demonstrate that the massless electrons in graphene can surprisingly exhibit a collective mass when subjected to a collective excitation, providing the inertia that is essential for the propagation of 2D plasmonic waves. Lastly, we theoretically investigate the thermal current fluctuation behaviors in massive and massless electron gases. While seemingly unrelated on first sight, we show that the thermal current fluctuation is actually intimately linked to the collective mass of the massive or massless electron gas. Thus, we show that the thermal current fluctuation behaviors can also be described by the same theoretical framework introduced earlier, suggesting a possibility to design new concept devices and experiments based on this linkage. / Engineering and Applied Sciences

Disertacijoje nagrinėjama, kaip padidinti susiaurintų spinduliuotės jutiklių jautrį. Taip pat disertacijoje siekiama ištirti mikrobangų spinduliuotės poveikį susiaurintiems puslaidininkiniams dariniams ir atskleisti stebimų efektų fizinę prigimtį bei nustatyti bandinių struktūros įtaką detektuojamo signalo dydžiui. Darbe sprendžiami tokie pagrindiniai uždaviniai: tiriamos įvairialyčių susiaurintų puslaidininkinių darinių savybės, priklausančios nuo darinių sluoksnių kokybės ir puslaidininkinių medžiagų parametrų bei analizuojamos savybės, priklausančios nuo stipriai legiruoto puslaidininkinio sluoksnio laidumo, nuo skiriamojo sluoksnio storio ir nuo sklendės pobūdžio metalizacijos. Siekiant užsibrėžto tikslo, buvo gaminami ir tiriami susiaurinti skirtingi įvairialyčiai dariniai (AlGaAs/GaAs, AlGaAs/InGaAs/GaAs) ir n-GaAs dariniai. Disertaciją sudaro penki skyriai, kurių paskutinis – rezultatų apibendrinimas. Pirmajame (įvadiniame) skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis darbo naujumas, pristatomi autoriaus pranešimai, disertacijos struktūra. Antrasis skyrius skirtas literatūros apžvalgai. Jame apžvelgiami elektromagnetinės spinduliuotės detektavimo principai, aptariamos šiluminės ir bigradientinės elektrovaros susidarymo priežastys, AlGaAs/GaAs įvairialytė sandūra, selektyvusis legiravimas bei puslaidininkinių prietaisų fizikinės galimybės. Trečiajame skyriuje pateikta eksperimento tyrimo metodika. Išsamiai... [toliau žr. visą tekstą] / The thesis presents the investigation on how to increase the sensitivity of the narrowed sensors of radiation. Also the thesis also deals with the attempts to analyze the influence of the microwave radiation on to the narrowed semiconductor formations and to reveal the physical nature of the observed effects as well as to determine the influence of structure of the samples on the detected signal magnitude. The work solves the following major tasks: the characteristics of the narrowed semiconductor heterostructures depending on the quality of the modulation layers and on the parameters of the semiconductor materials as well as the characteristics, depending on the selectively doped structure, on the conductivity of the highly doped semiconductor layer, and on the thickness of the separating layer, and the type of metallization of the gate. In order to achieve the goal there were produced and investigated narrowed different heterostructures (AlGaAs/GaAs, AlGaAs/InGaAs/GaAs) and n-GaAs structures. The thesis consists of four chapters, the final one is the generalization of the results. The first chapter (introductory) deals with the actuality of the problem, the aim and the tasks are stated, the novelty of the scientific research is described, the reports of the author are presented together with the publications, and the structure of the thesis. The second chapter is assigned to the review of the literature. It presents the principals of electromagnetic radiation detection... [to full text]

The thesis presents the investigation on how to increase the sensitivity of the narrowed sensors of radiation. Also the thesis also deals with the attempts to analyze the influence of the microwave radiation on to the narrowed semiconductor formations and to reveal the physical nature of the observed effects as well as to determine the influence of structure of the samples on the detected signal magnitude. The work solves the following major tasks: the characteristics of the narrowed semiconductor heterostructures depending on the quality of the modulation layers and on the parameters of the semiconductor materials as well as the characteristics, depending on the selectively doped structure, on the conductivity of the highly doped semiconductor layer, and on the thickness of the separating layer, and the type of metallization of the gate. In order to achieve the goal there were produced and investigated narrowed different heterostructures (AlGaAs/GaAs, AlGaAs/InGaAs/GaAs) and n-GaAs structures. The thesis consists of four chapters, the final one is the generalization of the results. The first chapter (introductory) deals with the actuality of the problem, the aim and the tasks are stated, the novelty of the scientific research is described, the reports of the author are presented together with the publications, and the structure of the thesis. The second chapter is assigned to the review of the literature. It presents the principals of electromagnetic radiation detection... [to full text] / Disertacijoje nagrinėjama, kaip padidinti susiaurintų spinduliuotės jutiklių jautrį. Taip pat disertacijoje siekiama ištirti mikrobangų spinduliuotės poveikį susiaurintiems puslaidininkiniams dariniams ir atskleisti stebimų efektų fizinę prigimtį bei nustatyti bandinių struktūros įtaką detektuojamo signalo dydžiui. Darbe sprendžiami tokie pagrindiniai uždaviniai: tiriamos įvairialyčių susiaurintų puslaidininkinių darinių savybės, priklausančios nuo darinių sluoksnių kokybės ir puslaidininkinių medžiagų parametrų bei analizuojamos savybės, priklausančios nuo stipriai legiruoto puslaidininkinio sluoksnio laidumo, nuo skiriamojo sluoksnio storio ir nuo sklendės pobūdžio metalizacijos. Siekiant užsibrėžto tikslo, buvo gaminami ir tiriami susiaurinti skirtingi įvairialyčiai dariniai (AlGaAs/GaAs, AlGaAs/InGaAs/GaAs) ir n-GaAs dariniai. Disertaciją sudaro penki skyriai, kurių paskutinis – rezultatų apibendrinimas. Pirmajame (įvadiniame) skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis darbo naujumas, pristatomi autoriaus pranešimai, disertacijos struktūra. Antrasis skyrius skirtas literatūros apžvalgai. Jame apžvelgiami elektromagnetinės spinduliuotės detektavimo principai, aptariamos šiluminės ir bigradientinės elektrovaros susidarymo priežastys, AlGaAs/GaAs įvairialytė sandūra, selektyvusis legiravimas bei puslaidininkinių prietaisų fizikinės galimybės. Trečiajame skyriuje pateikta eksperimento tyrimo metodika. Išsamiai... [toliau žr. visą tekstą]

A systematic and detailed design, building and testing of a high-sensitivity real-time magnetovision imaging system for non-destructive testing (NDT) was the purpose of the research presented here. The magnetic imaging systems developed were all based on an ultra-high sensitivity Quantum Well Hall Effect (QWHE) sensors, denoted as the P2A, which is based on GaAs-InGaAs-AlGaAs 2DEG heterostructures. The research progressed from 0D (single sensor) to 1D (linear array) to 2D (two dimensional arrays) testing modalities. Firstly, the measurement of thermal and shot noises, drift, detection limit, and dynamic offset cancellation of the QWHE sensor were studied in detail to set the framework and limitations of the fundamental QWHE sensors before their eventual use in the imaging systems developed subsequently. The results indicate that the measured data agrees well with calculations for thermal and shot noise when the input bias current is < 3 mA. The measured drift voltages of various QWHE sensors (P2A and P3A) are less than 200 µV when the sensor bias voltage is less than or equal to 2 V. A 4-direction dynamic offset cancellation technique was developed and the results show that the offset equivalent magnetic field of the QWHE sensors can be reduced from ~ 1mT to readings equal to the Earth magnetic field (~ 50 µT). Secondly, a flexible 16 × 1 array and a 32 × 2 staggered array magnetic-field scanners were designed, built, and tested. The QWHE magnetometer had a field strength resolution of 100 nT, and a measurement dynamic range of 138 dB. The flexible 16 × 1 magnetic field scanner can be used to test uneven and/or curved surfaces. This gives the flexible magnetic field scanner better inspection capabilities in both welding hump and circular pipe samples. By the staggered arrangement of two sensor arrays, a 15.4 point per inch horizontal spatial resolution can be achieved for the staggered 32 × 2 magnetic field scanner. Both direct and alternating magnetic flux leakage (DC and AC MFL) tests with the QWHE magnetometer were accomplished to obtain graphical 2-dimensional magnetic field distributions. Both the shape and the location of defects can be identified. The results show that the sensor has high sensitivity and linearity in a wide frequency range which makes it an optimum choice for AC-MFL testing and both ferromagnetic and non-ferromagnetic materials can be investigated. Thirdly, real-time 8 × 8 and 16  16 QWHE array magnetic-field cameras were designed, built, and tested. These prototypes can measure static magnetic field strengths in a 2-dimensional plane. Different shapes of magnets and magnetic field polarities can all be identified by the 8 × 8 magnetic field camera. The camera has a resolution of 3.05 mT, and a dynamic range of 66 dB (the minimum and maximum fields measurable are 3.05 mT and 6.25 mT) and a real time magnetic field measurement rate of 13 frames per second (FPS). By contrast the1616 array magnetic field camera has an improved sampling rate of 600 frame per second and with the use of an interpolation technique, a spatial resolution of 40.6 point per inch can be achieved. The minimum and maximum detectable magnetic field for this magnetic field camera are 1.8 µT and 29.5 mT respectively leading to a record dynamic range of 84 dB for high quality imaging. Finally, a novel, hand held, magnetovision system based on the real-time 16 × 16 QWHE array magnetic-field camera was developed for improved DC and AC electromagnetic NDT testing. The system uses a new super heterodyne technique for data acquisition using the QWHE sensor as a multiplier. This is the first report of such a technique in Hall effect magnetometry. The experimental results of five case studies demonstrate that the defects location and shape can be successfully measured with MFL in DC and AC magnetic field configurations including depth profiling. The major advantages of this real-time magnetic-field camera are: (1) its ease to use as a MFL testing equipment in both DC and AC NDT testing, (2) its ability to provide 2D graphical images similar to Magnetic Particle Inspection (MPI) but without its inherent health and safety drawbacks, (3) its capability to test both ferromagnetic and non-ferromagnetic materials for deep defects below the surface using low frequency alternating magnetic fields, and (4) its ability to identify materials (metals) by alternating external magnetic field illuminations, which has considerable potential in several applications such as security checking and labelling, magnetic markers for analysis, bio-imaging detection, and medical treatments amongst others.

Contemporary diagnostics rely on expensive, time-consuming, and optically-limited mechanisms that prevent at-home point-of-care molecular diagnostics with the accuracy of laboratory tools and the convenience of affordability. In this Thesis, biosensing was explored with commercial two-dimensional (2D) materials which have been investigated extensively over the last two decades yielding a variety of sensor metrics for detecting biomolecules. 2D materials have intrinsic properties that depend on the quality of material and substrate surface being employed. Here, graphene/SiO2 and monolayer hexagonal boron nitride (hBN) capping layer on graphene/SiO2 field-effect transistors (FETs) were used. Until recently, monolayer hBN has not been commercially available at the wafer-scale and has been observed in the literature to augment the properties of graphene-based devices and better control of processing repeatability. The work in this Thesis combines biochemistry with the wafer-scale production and surface-dependent properties of graphene and monolayer hBN/graphene via a FET fabrication process circumventing the use of photoresist. This was done to avoid photoresist resin that may contaminate the transducer surface and contribute to repeatability issues when studying biochemistry with 2D materials. Briefly, surface engineering of graphene/SiO2 and hBN/graphene/SiO2 was done, and the transfer characteristics were measured as a function of either the concentration of protons, genes, or proteins. Compared to bare 2D materials, the pH sensitivity of the shift in Dirac voltage was enhanced to -99 mV/pH when using 8.6 nm of Al2O3 on hBN/graphene/SiO2 FET. Graphene devices were then engineered for sensing SARS-CoV-2 genome with a signal-to-noise ratio of 3 at 100 aM and a linearized sensitivity of +22 mV/molar decade of SARS-CoV-2 ribonucleic acid and a dynamic range of four orders of magnitude. This was done by conjugating single-stranded deoxyribonucleic acid to sub-percolation threshold gold nanofilms deposited directly on the graphene sensing mesa. Finally, the 2D devices were studied for detecting SARS-CoV-2 spike protein after being functionalized with rabbit immunoglobulin G (IgG) monoclonal antibody (mAb). Additionally, preliminary work was done regarding the partial reduction and fragmentation of anti-SARS-CoV-2 spike protein human mAb IgG in an approach to leverage gold-thiol chemistry for covalently bonding the IgG to the 2D sensing mesa. In summary, the utilization of wide- and zero-bandgap nanomaterials may have profound implications in augmenting molecular diagnosis and treatment of disease through economically decentralizing biosensing. / 2024-01-20T00:00:00Z

No description available.

Le travail de thèse effectué porte sur la caractérisation électrique et la modélisation du gaz d’électrons à deux dimensions (2D) dans les dispositifs MOS-HEMT à base de l’hétérojonction AlGaN/AlN/GaN. Ces dispositifs ont un fort potentiel pour les applications d'électronique de puissance. Ce travail de recherche se place en soutien aux efforts de recherche pour l’élaboration des épitaxies GaN sur Si et pour les filières technologiques HEMT sur GaN. Il s'agit de comprendre précisément le fonctionnement du gaz d'électrons 2D et ses propriétés de transport électronique. Une nouvelle méthodologie a été développée pour identifier le dopage résiduel de la couche GaN, lequel est un paramètre important des substrats GaN et était par ailleurs difficile à évaluer. Un deuxième axe de recherche a consisté à proposer des techniques de mesure fiables ainsi qu’une modélisation des propriétés de transport du gaz d'électrons 2D. Dans ce cadre, des mesures split-CV et effet Hall ont été réalisées en fournissant pour chacune d’elles un protocole expérimental adéquat, avec un montage innovant pour les mesures effet Hall. Ce travail expérimental a été enrichi par une modélisation des propriétés du transport du 2DEG basée sur le formalisme de Kubo-Greenwood. Enfin, dans un dernier axe de recherche, un aspect plus général visant la compréhension en profondeur de l’électrostatique de l’empilement de la grille de nos GaN-MOS-HEMT a été proposé. Il est basé sur la caractérisation électrique C-V, la modélisation et l’extraction des paramètres. Le modèle développé a permis de souligner l'impact des charges surfaciques de polarisation et des défauts sur la tension de seuil des MOS-HEMT. Ce modèle a également permis d’estimer une valeur de la déformation dans les couches GaN épitaxiées sur un substrat Silicium. / This thesis aims at studying the electrical characterization and modelling of two-dimensional (2D) electron gas in MOS-HEMT devices based on the hetero-junction AlGaN/AlN/GaN. These devices are very promising candidates for power electronics applications. This research work provides the production team with detailed data on phenomena affecting GaN material. The goal is to understand precisely how 2D electron gas works and evaluate its electronic transport properties. A new methodology has been developed to identify residual doping of the GaN layer. This method was developed in order to answer a real need to know this doping to determine the quality of the epitaxial GaN layer. The second research priority was to provide reliable measurement techniques and modelling of the transport properties of 2D electron gas. Within this framework, the split-CV and Hall effect measurements were carried out by providing for each of them a suitable experimental protocol, with an innovative set-up for Hall effect measurements. In addition, this experimental work was supported by modelling the transport properties of 2DEG based on Kubo-Greenwood's formalism. Finally, a more general aspect aimed at an in-depth understanding of the electrostatic stacking of the GaN-MOS-HEMT gate. It is based on C-V electrical characterization, modelling and parameter extraction. The model developed made it possible to highlight the impact of polarization surface charges and defects on the threshold voltage of MOS-HEMT. This model also contributed to the estimation of the value of deformation in epitaxial GaN layers on a Silicon substrate.

L’étude des symétries d’un système peut en révéler de nombreuses propriétés physiques. La brisure, spontanée ou non, d’une de ces symétries implique alors d’importantes conséquences sur le comportement du système. On le voit dans la description actuelle de la physique des particules, avec notamment la création de la masse, ou dans la physique des solides, domaine de cette thèse, avec l’apparition de phases aux propriétés diverses, comme le magnétisme ou la supraconductivité. Le présent travail étudie par spectroscopie de photoémission résolue en angle (ARPES) les effets d’une brisure de symétrie dans deux systèmes différents : le système de fermions lourds URu2Si2 et l’oxyde de métal de transition (TMO) KTaO3. Le cristal d’URu2Si2 passe d’une phase paramagnétique pour T>THO, sujette à la cohérence de Kondo, vers la phase dite d’ordre caché pour T<THO, avec THO ≈ 17.5 K, brisant potentiellement plusieurs symétries. Bien qu’il y a presque trente ans que cettetransition de phase fut mesurée expérimentalement, aucun modèle théorique n’a encore réussi à faire consensus dans la communauté. Malgré une caractérisation expérimentale désormais très poussé de ce système, des informations résolues en angle manquent cruellement pour la compréhension de cette mystérieuse phase. Ce travail de thèse utilise donc des installations ARPES pour mettre en évidence, entre autre, le gap d’ordre caché, d’une amplitude inférieure à 10 meV. Nous montrons que ces mesures s’accordent avec plusieurs travaux expérimentaux précédents. Finalement, nous trouvons de fortes similarités entre les dispersions mesurées et celles calculées par LSDA, soulignant toutefois la nécessité d’introduire une renormalisation importante des masses effectives. Ce résultat contraint fortement les futures modélisations du comportement électronique de l’URu2Si2, tranchant sur l’approche à adopter.Contrairement au dernier système, où nous étudions une transition de phase, dans le tantalate de potassium KTaO3, notre attention se porte sur la brisure de symétrie de translation provoquée par la surface (111). Faisant suite à des mesures de transport qui revélèrent l’existence d’un gaz d’électron bidimensionnel (2DEG) à l’interface d’une hétérostructure de deux TMOs isolants de bandes, notre groupe mesura, plus tard, des 2DEGs aux surfaces (001) nues de SrTiO3 et de KTaO3, par ARPES. C’est dans la continuité de ces résultats que se place le présent travail, avec le désir d’élargir les caractéristiques de ces 2DEGs. Ainsi, poussé par la prédiction théorique d’état au caractère topologique non-trivial, nous apportons l’évidence d’un 2DEG à la surface (111) de KTaO3. Nous modélisons ensuite avec succès sa dispersion particulière grâce à des calculs de liaisons fortes. Ce travail constitue une étape dans la possible mise en évidence d’états au caractère topologique non-trivial dans les TMOs. / Several physical properties of a system can be understood by looking at the symmetries involved. Breaking of a symmetry affects the behavior of the system, regardless ifit happens spontaneously or not. This is observed with the emergence of the mass inparticle physics models, or with the diverse phases arising in condensed matter systems,as magnetism or superconductivity. Using angle-resolved photoemission spectroscopy (ARPES), this work studies theeffects of a symmetry breaking for two different systems : the heavy fermion systemURu2Si2 and the transition metal oxide (TMO) KTaO3. In URu2Si2, a transition occurs from a paramagnetic phase at T>THO to the hiddenorder phase at T<THO, with THO ≈ 17.5 K. This new order potentially breaks several symmetries. Although this transition was measured almost thirty years back, usingelectrical transport, no theoretical model could yet bring a consensus in the community. Since then, various characterizations of this system have been realized, howevermomentum-resolved informations are still missing to help unravel this mystery. Thus,during this thesis, we used state-of-the-art ARPES setups to measure several gaps located at different points in the Brillouin zone, and with amplitudes below 10 meV. Someof them are related to the Kondo coherence, and one is the hidden order gap. We showthat these measurements are consistent with previous experimental works. Finally, weobserved that our measurements differ from LSDA calculations solely by a renormalization of the effective masses by, at least, a factor 10 close to the Fermi level. Taking intoaccount some interactions, such as electronic ones, could lead to a more accurate model.Our measurements provide the constraints for this possible modeling. Unlike the transition we just described, the symmetry breaking in potassium tantalate KTaO3 is not spontaneous. In this system, we look at the (111) surface, wherethe translation symmetry is broken. A metallic two-dimensional electron gas (2DEG)has been measured in 2004 by Ohtomo at the interface between two insulating TMOs :strontium titanate SrTiO3 and lanthanum aluminate LaAlO3. The possible electronicapplications of exotic properties in TMOs, resulting from the d orbitals, has brought anew wave of activity to this topic. Later, our group measured 2DEGs at the (001) baresurfaces of SrTiO3 and KTaO3. Following these results, we wished to tailor the characteristic of such 2DEGS. Led by the theoretical prediction of states with non-trivialtopological character, we are presenting the evidence of a 2DEG at the (111) surface ofKTaO3. We also discuss its dispersion and introduce a tight binding calculation modelsuccessfully. This work is a step towards the realization of non-trivial topological statesin transition metal oxides.