Harry Alles - Profile on Academia.edu (original) (raw)

Papers by Harry Alles

IOP Conference Series: Materials Science and Engineering, 2013

Seed-layer approach was studied to initiate atomic layer deposition (ALD) of Al2O3 films on graph... more Seed-layer approach was studied to initiate atomic layer deposition (ALD) of Al2O3 films on graphene. Low-temperature ALD and electron beam evaporation (EBE) were applied for seed-layer preparation before deposition of the dielectric at 200 o C using trimethylaluminum and water or ozone as precursors. To characterize nucleation of the films and possible influence of the ALD processes on the quality of graphene, properties of graphene and Al2O3 films were investigated by Raman spectroscopy, X-ray fluorescence and X-ray photoelectron spectroscopy methods. The results suggest that seed layer formation by lowtemperature ALD was more efficient in the O3-based process than in the H 2 O-based one while EBE seed layer provided fastest growth of Al2O3 together with minimum incubation period.

Sensors and Actuators B: Chemical, 2014

We have synthesized single-layer graphene on Cu foils using chemical vapor deposition method and ... more We have synthesized single-layer graphene on Cu foils using chemical vapor deposition method and transferred the graphene to the top of a Si/SiO 2 substrate with a pair of prefabricated Ti/Au electrodes. A resistive graphene-based gas sensor prepared in this way revealed n-type oxygen response at room temperature and we have successfully fitted the data obtained with varying oxygen levels using a two-site Langmuir model. p-Type oxygen response of our sensor was observed after the temperature was raised to 100 • C, with a reversible transition to n-type behavior when the temperature was lowered back to room temperature. Such inversion of the gas response type with temperature was interpreted as a result of interplay between the adsorbate-induced charge transfer and charge carrier scattering. The transduction function was derived, which relates the electrical response to surface coverage through both the induced mobility and charge density changes.

Measurements on the melting curve of ^4He down to 10 mK

Recent discovery of a nonclassical rotational inertia in solid ^4He below about 0.2 K by Kim and ... more Recent discovery of a nonclassical rotational inertia in solid ^4He below about 0.2 K by Kim and Chan has initiated an intensive study on the properties of solid ^4He. As Kim and Chan have interpreted their observation as the evidence of supersolid behavior, we have decided to measure very accurately the melting curve of ^4He because, as the slope of the melting curve is proportional to the difference in the entropy of the liquid and solid phases, there should be an anomaly at the possible supersolid transition. We have measured the melting curve of ^4He with the accuracy of about 0.5 microbar with ^4He crystals which had various concentration of defects. All our samples showed only the expected T^4 dependence due to phonons without any sign of the supersolid transition in the temperature range of 80400 mK. Below 80 mK we observed a small deviation from T^4 dependence which, however, cannot be attributed to the supersolid transition because our recent measurements with the cell cont...

Jetp Lett Engl Tr, Mar 28, 2007

We have measured the melting pressure and pressure in the liquid at constant density of ultra-pur... more We have measured the melting pressure and pressure in the liquid at constant density of ultra-pure 4^44He (0.3 ppb of 3^33He impurities) with the accuracy of about 0.5 mu\mumubar in the temperature range from 10 to 320 mK. Our measurements show that the anomaly on the melting curve below 80 mK which we have recently observed is entirely due to an anomaly in the elastic modulus of Be-Cu from which our pressure gauge is made of. We thus conclude that the melting pressure of 4^44He follows the T4T^4T4 law due to phonons in the whole temperature range from 10 to 320 mK without any sign of a supersolid transition.

Faceting of He-3 crystals

Physica B-condensed Matter, 2000

Torsional oscillator and NMR measurements on superfluid 3He in aerogel glass of 98% porosity are ... more Torsional oscillator and NMR measurements on superfluid 3He in aerogel glass of 98% porosity are compared with predictions of the homogeneous scattering model in the Ginzburg–Landau limit for the B-phase; ρs is less than predicted but semi-quantitative agreement between experiment and theory is obtained for the NMR data.

Reviews of Modern Physics, 2005

Helium crystals exhibit faceting as do ordinary crystals, but no other crystals can grow and melt... more Helium crystals exhibit faceting as do ordinary crystals, but no other crystals can grow and melt sufficiently fast to make the propagation of crystallization waves possible at their surfaces. After nearly two decades of controversy, it is now generally accepted that helium crystals are model systems for the general study of crystal surfaces, but also exceptional in having unique quantum properties. This review, which summarizes 25 years of research on the surface of helium crystals, treats both what is general and what is particular to helium. A central issue among the general properties is the "roughening transition," the phase transition from a smooth faceted state of the crystal surface at low temperature to a rough and fluctuating state at high temperature. This review describes the series of experiments that have significantly improved our understanding of this transition and its related critical phenomena. Some attention is paid to the experimental techniques, which are rather unusual in many cases. The Nozières renormalization theory of roughening is also described in some details and compared with experiment. Other general properties of crystal surfaces have also been studied in helium, such as the energy of steps on the facets and their mutual interactions, and several instabilities. The relevant experiments are presented together with their theoretical interpretation. The quantum mechanisms that control the growth dynamics of helium crystals are also reviewed. Here, too, theory is compared with experiment, not only in the matter of crystallization waves, but more generally on the mass and heat flows in nonequilibrium situations, including the two stable helium isotopes 4 He and 3 He, which behave in quite different ways. Finally, a list of open questions is presented for future research.

Physical Review Letters, 1994

Optical interferometry at ultra low temperatures

Journal of Low Temperature Physics, 1995

ABSTRACT We have developed optical, interferometric methods for investigations of interfaces at u... more ABSTRACT We have developed optical, interferometric methods for investigations of interfaces at ultra low temperatures. In our scheme conventional optical windows are avoided: laser illumination (He-Ne) is guided into the cryostat via a single-mode optical fiber and images are taken using a CCD sensor mounted inside the 4-K vacuum can. A real-time video camera has been successfully used in investigations of superfluid3He down to 0.6 mK whereas a slow-scan camera has been employed for optimal contrast in low-intensity imaging of liquid/solid interfaces (reflection coefficient 10–6). The investigated topics include (1) superfluid3He surface in rotation and during rapid deceleration, (2) hydrodynamics of thin superfluid3He layers, (3) superfluid/solid interface in4He, and (4) wetting of superfluid4He by normal3He in phase separated mixtures. A vertical resolution of 10 nm and even below has been achieved in these studies.

Journal of Low Temperature Physics, 2000

Metastability and hysteresis of the vortex states in rotating superfluid3He-B

Czechoslovak Journal of Physics, 1996

We have investigated the vortex core transition in3He-B by measuring the associated changes in mu... more We have investigated the vortex core transition in3He-B by measuring the associated changes in mutual fricition dissipation within the superfluid. If rotation is continuously stopped and restarted while cooling or warming then the transition occurs at a clearly defined temperature, but temperature sweeps during continuous rotation show substantial supercooling and superheating. Moreover, the high temperature vortex shows a continuum of metastable states when supercooled to a constant, arbitrary low temperature, the mutual friction dissipaton depending on the temperature at which rotation was started. Our current interpretation is that the high temperature vortex state is a temperature-dependent mixture of two vortex types.

Phys Rev Lett, 2004

3 He crystals start to show facets on their surface only at about 100 mK, well below the rougheni... more 3 He crystals start to show facets on their surface only at about 100 mK, well below the roughening transition temperature. To understand the reason for that, we have performed the first quantitative investigation on the growth dynamics of the basic (110) facet at 60 -110 mK. The obtained values of the step free energy suggest an extremely weak coupling of the solid-liquid interface to the crystal lattice which we show to be the result of quantum fluctuations of the interface. The renormalization group approach by Nozières and Gallet, modified to incorporate quantum fluctuations, explains well the temperature dependence of the step energy measured in this work and at ultralow temperatures by Tsepelin et al., where the coupling is known to be strong. We have thus shown that, paradoxically, the role of quantum fluctuations is at higher temperatures much larger than at low temperature.

Raman characterization of stacking in multi-layer graphene grown on Ni

Carbon, 2015

Physical Review Letters

According to Landau, at T=0 the equilibrium crystal surface consists of an infinite number of fac... more According to Landau, at T=0 the equilibrium crystal surface consists of an infinite number of facets lying in all directions with rational Miller indices-the so-called devil's staircase phenomenon. We have discovered 11 new types of facets on the surface of 4He crystals, in addition to the three observed before. Some of the new facets are of very high order, lying at angles as small as 4 degrees to the basal c facet, thus forming the predicted devil's staircase. The estimated step energies depend rather weakly on interplanar distance which we explain by the strong anisotropy of the steps.

Physica B: Condensed Matter, 1992

We report on progress in a prestudy concerning the possibility of performing optical imaging of t... more We report on progress in a prestudy concerning the possibility of performing optical imaging of the free surface of rotating superfluid 3He, General problems of optical experiments at milliKelvin temperatures are discussed. Measurements of heat loads caused by illumination and thermal radiation are described.

Experimental investigation of two-phonon absorption by the real squashing mode in superfluid 3He-B

Physica B: Condensed Matter, 1992

... Rev. Lett. 45 (1980) 1952. [10] BS Shivaram, MW Meisel, BK Sarma, DB Mast, WP Halperin and JB... more ... Rev. Lett. 45 (1980) 1952. [10] BS Shivaram, MW Meisel, BK Sarma, DB Mast, WP Halperin and JB Ketterson, Phys. Rev. Lett. 49 (1982) 1646. [11] BS Shivaram, MW Meisel, BK Sarma, WP Hal-perin and JB Ketterson, J. Low Temp. Phys. 63 (1986) 57. ...

Discontinuity and misorientation of graphene grown on nickel foil: Effect of the substrate crystallographic orientation

Carbon, 2015

ABSTRACT See up to Aug. 18th: http://authors.elsevier.com/a/1RHZ11zUA1UN6

Thin Solid Films, 2014

Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe... more Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe 2 ) 3 and H 2 O, was investigated using real-time characterization of the growth process and post-growth measurements of the films. Self-limited nature of the deposition process was observed at substrate temperatures ranging from 120 to 350°C. In this temperature range growth rate of 0.08-0.1 nm per cycle was obtained on silicon substrates. The films deposited on silicon substrates at 200°C and higher temperatures contained tetragonal and monoclinic phases of ZrO 2 . The phase composition of the films depended on the deposition temperature as well as on the film thickness. The concentration of carbon residues decreased with increasing deposition temperature and did not exceed 0.9 at.% in the films deposited at 250°C and higher temperatures. The refractive indices and densities of films grown from CpZr(NMe 2 ) 3 and H 2 O at 250-350°C ranged from 2.15 to 2.20 (at a wavelength of 633 nm) and 5.6 to 6.0 g/cm 3 , respectively, being close to the highest values obtained for films deposited from ZrCl 4 and H 2 O. The former process ensured, however, more uniform nucleation of ZrO 2 on graphene than the latter process did.

Photo-activated oxygen sensitivity of graphene at room temperature

Applied Physics Letters, 2014

ABSTRACT Photo-induced changes in the electrical conductivity and the sensitivity to oxygen gas o... more ABSTRACT Photo-induced changes in the electrical conductivity and the sensitivity to oxygen gas of graphene sheets grown by chemical vapor deposition and transferred onto Al2O3 and SiO2 thin film substrates were studied at ambient conditions. The pristine graphene sensors were initially completely insensitive to oxygen gas at room temperature but showed significant (up to 100%) response when illuminated with weak ultraviolet (300 nm or 365 nm) light. Oxygen response was governed by Langmuir law and its activation was insensitive to humidity. The mechanism of sensitization is analyzed together with other photo-induced effects-negative persistent photo-conduction and photo-induced hysteresis of field effect transistor characteristics. While the reduction of conductivity in air is persistent effect, the oxygen sensitization and enlargement of hysteresis take place only under the direct influence of light. It is concluded that the charge traps with differently adsorbed oxygen and water are involved in these phenomena. (C) 2014 AIP Publishing LLC.

Proceedings of the National Academy of Sciences of the United States of America, Jan 19, 2002

It has been predicted by Landau that, ideally at low temperatures, crystals should show many diff... more It has been predicted by Landau that, ideally at low temperatures, crystals should show many different types of facets, i.e., flat smooth faces on their surface, but this so-called "devil's staircase" phenomenon has been difficult to observe experimentally. In this paper we describe our recent experiments, in which altogether 11 different types of facets have been identified on growing (3)He crystals at the temperature of 0.55 mK by using a unique low-temperature Fabry-Pérot interferometer. Previously only 3 types of facets had been seen in this system. We have also measured the growth velocities of different facets, and our interpretation of the obtained results yields the conclusion that (3)He has much stronger coupling of the liquid-solid interface to the crystal lattice than has been expected. After an introduction we present a short theoretical background about the equilibrium crystal shape and the roughening transitions, which is followed by the description of ou...

IOP Conference Series: Materials Science and Engineering, 2013

Seed-layer approach was studied to initiate atomic layer deposition (ALD) of Al2O3 films on graph... more Seed-layer approach was studied to initiate atomic layer deposition (ALD) of Al2O3 films on graphene. Low-temperature ALD and electron beam evaporation (EBE) were applied for seed-layer preparation before deposition of the dielectric at 200 o C using trimethylaluminum and water or ozone as precursors. To characterize nucleation of the films and possible influence of the ALD processes on the quality of graphene, properties of graphene and Al2O3 films were investigated by Raman spectroscopy, X-ray fluorescence and X-ray photoelectron spectroscopy methods. The results suggest that seed layer formation by lowtemperature ALD was more efficient in the O3-based process than in the H 2 O-based one while EBE seed layer provided fastest growth of Al2O3 together with minimum incubation period.

Sensors and Actuators B: Chemical, 2014

We have synthesized single-layer graphene on Cu foils using chemical vapor deposition method and ... more We have synthesized single-layer graphene on Cu foils using chemical vapor deposition method and transferred the graphene to the top of a Si/SiO 2 substrate with a pair of prefabricated Ti/Au electrodes. A resistive graphene-based gas sensor prepared in this way revealed n-type oxygen response at room temperature and we have successfully fitted the data obtained with varying oxygen levels using a two-site Langmuir model. p-Type oxygen response of our sensor was observed after the temperature was raised to 100 • C, with a reversible transition to n-type behavior when the temperature was lowered back to room temperature. Such inversion of the gas response type with temperature was interpreted as a result of interplay between the adsorbate-induced charge transfer and charge carrier scattering. The transduction function was derived, which relates the electrical response to surface coverage through both the induced mobility and charge density changes.

Measurements on the melting curve of ^4He down to 10 mK

Recent discovery of a nonclassical rotational inertia in solid ^4He below about 0.2 K by Kim and ... more Recent discovery of a nonclassical rotational inertia in solid ^4He below about 0.2 K by Kim and Chan has initiated an intensive study on the properties of solid ^4He. As Kim and Chan have interpreted their observation as the evidence of supersolid behavior, we have decided to measure very accurately the melting curve of ^4He because, as the slope of the melting curve is proportional to the difference in the entropy of the liquid and solid phases, there should be an anomaly at the possible supersolid transition. We have measured the melting curve of ^4He with the accuracy of about 0.5 microbar with ^4He crystals which had various concentration of defects. All our samples showed only the expected T^4 dependence due to phonons without any sign of the supersolid transition in the temperature range of 80400 mK. Below 80 mK we observed a small deviation from T^4 dependence which, however, cannot be attributed to the supersolid transition because our recent measurements with the cell cont...

Jetp Lett Engl Tr, Mar 28, 2007

We have measured the melting pressure and pressure in the liquid at constant density of ultra-pur... more We have measured the melting pressure and pressure in the liquid at constant density of ultra-pure 4^44He (0.3 ppb of 3^33He impurities) with the accuracy of about 0.5 mu\mumubar in the temperature range from 10 to 320 mK. Our measurements show that the anomaly on the melting curve below 80 mK which we have recently observed is entirely due to an anomaly in the elastic modulus of Be-Cu from which our pressure gauge is made of. We thus conclude that the melting pressure of 4^44He follows the T4T^4T4 law due to phonons in the whole temperature range from 10 to 320 mK without any sign of a supersolid transition.

Faceting of He-3 crystals

Physica B-condensed Matter, 2000

Torsional oscillator and NMR measurements on superfluid 3He in aerogel glass of 98% porosity are ... more Torsional oscillator and NMR measurements on superfluid 3He in aerogel glass of 98% porosity are compared with predictions of the homogeneous scattering model in the Ginzburg–Landau limit for the B-phase; ρs is less than predicted but semi-quantitative agreement between experiment and theory is obtained for the NMR data.

Reviews of Modern Physics, 2005

Helium crystals exhibit faceting as do ordinary crystals, but no other crystals can grow and melt... more Helium crystals exhibit faceting as do ordinary crystals, but no other crystals can grow and melt sufficiently fast to make the propagation of crystallization waves possible at their surfaces. After nearly two decades of controversy, it is now generally accepted that helium crystals are model systems for the general study of crystal surfaces, but also exceptional in having unique quantum properties. This review, which summarizes 25 years of research on the surface of helium crystals, treats both what is general and what is particular to helium. A central issue among the general properties is the "roughening transition," the phase transition from a smooth faceted state of the crystal surface at low temperature to a rough and fluctuating state at high temperature. This review describes the series of experiments that have significantly improved our understanding of this transition and its related critical phenomena. Some attention is paid to the experimental techniques, which are rather unusual in many cases. The Nozières renormalization theory of roughening is also described in some details and compared with experiment. Other general properties of crystal surfaces have also been studied in helium, such as the energy of steps on the facets and their mutual interactions, and several instabilities. The relevant experiments are presented together with their theoretical interpretation. The quantum mechanisms that control the growth dynamics of helium crystals are also reviewed. Here, too, theory is compared with experiment, not only in the matter of crystallization waves, but more generally on the mass and heat flows in nonequilibrium situations, including the two stable helium isotopes 4 He and 3 He, which behave in quite different ways. Finally, a list of open questions is presented for future research.

Physical Review Letters, 1994

Optical interferometry at ultra low temperatures

Journal of Low Temperature Physics, 1995

ABSTRACT We have developed optical, interferometric methods for investigations of interfaces at u... more ABSTRACT We have developed optical, interferometric methods for investigations of interfaces at ultra low temperatures. In our scheme conventional optical windows are avoided: laser illumination (He-Ne) is guided into the cryostat via a single-mode optical fiber and images are taken using a CCD sensor mounted inside the 4-K vacuum can. A real-time video camera has been successfully used in investigations of superfluid3He down to 0.6 mK whereas a slow-scan camera has been employed for optimal contrast in low-intensity imaging of liquid/solid interfaces (reflection coefficient 10–6). The investigated topics include (1) superfluid3He surface in rotation and during rapid deceleration, (2) hydrodynamics of thin superfluid3He layers, (3) superfluid/solid interface in4He, and (4) wetting of superfluid4He by normal3He in phase separated mixtures. A vertical resolution of 10 nm and even below has been achieved in these studies.

Journal of Low Temperature Physics, 2000

Metastability and hysteresis of the vortex states in rotating superfluid3He-B

Czechoslovak Journal of Physics, 1996

We have investigated the vortex core transition in3He-B by measuring the associated changes in mu... more We have investigated the vortex core transition in3He-B by measuring the associated changes in mutual fricition dissipation within the superfluid. If rotation is continuously stopped and restarted while cooling or warming then the transition occurs at a clearly defined temperature, but temperature sweeps during continuous rotation show substantial supercooling and superheating. Moreover, the high temperature vortex shows a continuum of metastable states when supercooled to a constant, arbitrary low temperature, the mutual friction dissipaton depending on the temperature at which rotation was started. Our current interpretation is that the high temperature vortex state is a temperature-dependent mixture of two vortex types.

Phys Rev Lett, 2004

3 He crystals start to show facets on their surface only at about 100 mK, well below the rougheni... more 3 He crystals start to show facets on their surface only at about 100 mK, well below the roughening transition temperature. To understand the reason for that, we have performed the first quantitative investigation on the growth dynamics of the basic (110) facet at 60 -110 mK. The obtained values of the step free energy suggest an extremely weak coupling of the solid-liquid interface to the crystal lattice which we show to be the result of quantum fluctuations of the interface. The renormalization group approach by Nozières and Gallet, modified to incorporate quantum fluctuations, explains well the temperature dependence of the step energy measured in this work and at ultralow temperatures by Tsepelin et al., where the coupling is known to be strong. We have thus shown that, paradoxically, the role of quantum fluctuations is at higher temperatures much larger than at low temperature.

Raman characterization of stacking in multi-layer graphene grown on Ni

Carbon, 2015

Physical Review Letters

According to Landau, at T=0 the equilibrium crystal surface consists of an infinite number of fac... more According to Landau, at T=0 the equilibrium crystal surface consists of an infinite number of facets lying in all directions with rational Miller indices-the so-called devil's staircase phenomenon. We have discovered 11 new types of facets on the surface of 4He crystals, in addition to the three observed before. Some of the new facets are of very high order, lying at angles as small as 4 degrees to the basal c facet, thus forming the predicted devil's staircase. The estimated step energies depend rather weakly on interplanar distance which we explain by the strong anisotropy of the steps.

Physica B: Condensed Matter, 1992

We report on progress in a prestudy concerning the possibility of performing optical imaging of t... more We report on progress in a prestudy concerning the possibility of performing optical imaging of the free surface of rotating superfluid 3He, General problems of optical experiments at milliKelvin temperatures are discussed. Measurements of heat loads caused by illumination and thermal radiation are described.

Experimental investigation of two-phonon absorption by the real squashing mode in superfluid 3He-B

Physica B: Condensed Matter, 1992

... Rev. Lett. 45 (1980) 1952. [10] BS Shivaram, MW Meisel, BK Sarma, DB Mast, WP Halperin and JB... more ... Rev. Lett. 45 (1980) 1952. [10] BS Shivaram, MW Meisel, BK Sarma, DB Mast, WP Halperin and JB Ketterson, Phys. Rev. Lett. 49 (1982) 1646. [11] BS Shivaram, MW Meisel, BK Sarma, WP Hal-perin and JB Ketterson, J. Low Temp. Phys. 63 (1986) 57. ...

Discontinuity and misorientation of graphene grown on nickel foil: Effect of the substrate crystallographic orientation

Carbon, 2015

ABSTRACT See up to Aug. 18th: http://authors.elsevier.com/a/1RHZ11zUA1UN6

Thin Solid Films, 2014

Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe... more Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe 2 ) 3 and H 2 O, was investigated using real-time characterization of the growth process and post-growth measurements of the films. Self-limited nature of the deposition process was observed at substrate temperatures ranging from 120 to 350°C. In this temperature range growth rate of 0.08-0.1 nm per cycle was obtained on silicon substrates. The films deposited on silicon substrates at 200°C and higher temperatures contained tetragonal and monoclinic phases of ZrO 2 . The phase composition of the films depended on the deposition temperature as well as on the film thickness. The concentration of carbon residues decreased with increasing deposition temperature and did not exceed 0.9 at.% in the films deposited at 250°C and higher temperatures. The refractive indices and densities of films grown from CpZr(NMe 2 ) 3 and H 2 O at 250-350°C ranged from 2.15 to 2.20 (at a wavelength of 633 nm) and 5.6 to 6.0 g/cm 3 , respectively, being close to the highest values obtained for films deposited from ZrCl 4 and H 2 O. The former process ensured, however, more uniform nucleation of ZrO 2 on graphene than the latter process did.

Photo-activated oxygen sensitivity of graphene at room temperature

Applied Physics Letters, 2014

ABSTRACT Photo-induced changes in the electrical conductivity and the sensitivity to oxygen gas o... more ABSTRACT Photo-induced changes in the electrical conductivity and the sensitivity to oxygen gas of graphene sheets grown by chemical vapor deposition and transferred onto Al2O3 and SiO2 thin film substrates were studied at ambient conditions. The pristine graphene sensors were initially completely insensitive to oxygen gas at room temperature but showed significant (up to 100%) response when illuminated with weak ultraviolet (300 nm or 365 nm) light. Oxygen response was governed by Langmuir law and its activation was insensitive to humidity. The mechanism of sensitization is analyzed together with other photo-induced effects-negative persistent photo-conduction and photo-induced hysteresis of field effect transistor characteristics. While the reduction of conductivity in air is persistent effect, the oxygen sensitization and enlargement of hysteresis take place only under the direct influence of light. It is concluded that the charge traps with differently adsorbed oxygen and water are involved in these phenomena. (C) 2014 AIP Publishing LLC.

Proceedings of the National Academy of Sciences of the United States of America, Jan 19, 2002

It has been predicted by Landau that, ideally at low temperatures, crystals should show many diff... more It has been predicted by Landau that, ideally at low temperatures, crystals should show many different types of facets, i.e., flat smooth faces on their surface, but this so-called "devil's staircase" phenomenon has been difficult to observe experimentally. In this paper we describe our recent experiments, in which altogether 11 different types of facets have been identified on growing (3)He crystals at the temperature of 0.55 mK by using a unique low-temperature Fabry-Pérot interferometer. Previously only 3 types of facets had been seen in this system. We have also measured the growth velocities of different facets, and our interpretation of the obtained results yields the conclusion that (3)He has much stronger coupling of the liquid-solid interface to the crystal lattice than has been expected. After an introduction we present a short theoretical background about the equilibrium crystal shape and the roughening transitions, which is followed by the description of ou...