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Schlom QS3 2018—Part I.Pptx Oxide MBE— A Tool to Create Artificial Quantum Materials Darrell G. Schlom Department of Materials Science and Engineering Cornell University Kavli Institute at Cornell for Nanoscale Science Outline • What is MBE and what is it good for? Greatest hits of MBE • How to grow your favorite oxide quantum material by MBE? Nuts and bolts of oxide MBE • Oxide MBE growth of quantum materials Case studies—including Sr2RuO4 • How can I gain access to an oxide MBE if I don’t have one? Use PARADIM’s oxide MBE (+ ARPES + ...) MBE ≈ Atomic Spray Painting 2264 ]. R. ARTHUR evaporation may be congruent, i.e. the tempera- in X As' and since aGa -J> 1 as X AS -J> 0 it is un- ture at which FGa = 2FAS.+4PAs4' is decreased likely that aGa is different from unity below slightly to 9100 K from Thurmond's estimate of 1200oK, the upper limit of our experiment. The 933°K. YGa calculations using equation (12) support this When GaAsWhile the isabsolute HeatedGa pressure could not be contention.… established accurately from the Ga + ion current, The log Y vs. X AS data in Fig. 4 are qualitatively J. Phys. Chem. Solids Pergamon Press 1967. Vol. 28, pp. 2257-2267. Printed in Great Britain. VAPOR PRESSURES AND PHASE EQUILIBRIA IN THE Ga-As SYSTEM J. R. ARTHUR Bell Telephone Laboratories, Incorporated, Murray Hill, New Jersey (Received 9 March 1967; in revisedform 18 May 1967) Abstract-Mass spectrometric and weight loss measurements of the species effusing from a Knudsen cell containing GaAs were used to obtain vapor pressures over the temperature range 900-1200oK. The As2 /As4 ratio was observed in these measurements to be substantially larger than previously reported(2.3) when precautions were taken to prevent the buildup of arsenic vapor in the mass spectrometer ionization chamber. A third law treatment of the data gave enthalpies for the reactions: GaAs(.) ->- Ga(.) + tAs2(,) ilH29SO = 44'9 kcal GaAs(.) ->- Ga(s) + tAs4 (,) ilH29So = 29·4 kcal 2As2(,) ->- As4 (,) ilH29SO = -62·5 kcal GaAs(S) ->- Ga(,) + As(,) ilH29So = 155 kcal -5 These results were used to correct Thurmond's calculations of vapor pressures and activity coeffi- cients along the GaAs liquidus. (1) -8 INTRODUCTION values for the free energy function (F O-H O)/T T 29S -7 THURMOND(l) has constructed the P-T curves from GaAs heat capacity data, (7) standard enthalpies along the binary GaAs liquidus using mass were calculated by a Third Law treatment for the spectrometric information by DROWART and reactions: -8 GOLDFINGER(2) and by GUTBIER, (3) total pressure GaAs(s) -'?- Ga(S) +!As (g) measurements near the GaAs m.p. by RICHMAN,(4) 2 and solubility data by KOSTER and THOMA (5) and IlH29S0 = 44·9 ± 0·5 kcal (1) -9 HALL. (6) Thurmond noted that the pressure GaAs(s) -'?- Ga(S) +lAs (g) measurements of Drowart and Goldfinger were 4 inconsistent with the high temperature measure- IlH29so = 29·4 ± 0·7 kcal (2) ments of Richman; furthermore the considerable 2As2(g) -'?- AS4(g) disagreement in the values for decomposition enthalpy obtained by mass analysis of decomposi- IlH29SO = - 62·5 ± 1·5 kcal (3) FIG. 5. Equilibrium vapor pressures of As, As2 , As. and tion products (see Table 1) made further studies GaAs(5) -'?- Ga(g) + AS(g) of low temperature decomposition seem desirable. Ga along the binary liquidus as a function of T - '. IlH O = 155 ± 2 kcal (4) We have used a mass spectrometer to determine 29S Pressures of AS 2 and As. over pure solid and liquid As the temperature dependence of the pressure of Using the new data, the pressure-temperature are also shown. As2, As4 and Ga over GaAs as well as the As2/ As4 curves along the Ga-As liquidus were recalculated ratio. Using weight loss measurements to cali- and found to be completely consistent with Rich- brate mass spectrometer sensitivity, vapor pres- man's high temperature data. P pGao, sures for the three species were determined from there was other evidence that Ga = the similar to Thurmond's results except that the 900-1200oK. When care was taken to prevent the EXPERIMENTALpressure over pure Ga. In the temperature range minimum in log YAs which Thurmond found near buildup of arsenic in the ionization chamber, the Figure 1 shows the Knudsen cell and mass of our data the arsenic atom fraction in liquid Ga X As = 0·03 is absent. Since As2/As4 ratio was found to be much larger than spectrometer ionization chamber. The EAr Quad that observed by previous workers.(2.3) Using new 200 quadrupole massincreased spectrometer from was -10-equipped3 to 4 x 10 - 2(6) yet no de- I1Fle !:lDl I1S e 2257 parture from linearity is evident in either arsenic l or gallium pressure data in Fig. 3. Furthermore, lnYAs = RT = RT - R (13) the temperature dependence of (IGa + T) indicated a second law heat of vaporization !:lHTo = 63·6 where !:lFle and !:lSIe are the partial molar excess kcal/mole, in agreement with value obtained free energy and entropy of mixing, respectively, by Munir and Searcy for pure Ga. Thus and !:llil is the partial molar heat of mixing, aGa = PGa/PGao is constant for a 40-fold increase Thurmond pointed out that the minimum in 438 LAMOREAUX, HllDENBRA",D, AND BREWER -1 -1 -3 -3 -5 -5 -7 -7 § -9 -9 438 LAMOREAUX, HllDENBRA",D, AND BREWER -11 -11 -1 -1 -13 -13 -3 -3 BOO 1000 1200 1400 1600 1800 T (K) T (1<) -5 -5 15 FIG. 53. PbO vaporization in 10-15 bar O2 below 905 K and vaporization of FIG. 56. PbO maximum vaporization rates. A_IO- bar 02; B-Ph-PbO -7 Ph-PbO mixture above 905 K. -7 equilibrium; C--congruent vaporization; D-D.2 bar O2 , § -9 -9 value seems somewhat large, calculations using the resulting thermodynamic properties are in excellent agreement with -1 -11 -11 Drowart's gas phase equilibria over the temperature range of measurements. Equilibrium data are available for PbsOs and -3 -13 -13 Pb60 6 at only one temperature, 1200 K. The entropy at 298 438 Consider Evaporation of PbO LAMOREAUX, HllDENBRA",D, AND BREWER K for these two species was estimated by extrapolating the -5 °2 values for the monomeric through tetrameric species, and BOO 1000 1200 1400 1600 1800 &: T (K) T (1<) the estimated value C;IR = 3.0 was used to calculate val- e -7 -1 -1 ues of the Gibbs energy functions. The gas phase equilibria at t!I 0 15 10-15 -' FIG. 53. PbO vaporization in bar O2 below 905 K and vaporization-9 of FIG. 56. PbOPb0 2maximum vaporization rates. A_IO-1200 Kbar were 02; B-Ph-PbOthen used to derive values of the enthalpies of -3 Ph-PbO mixture above 905-3 K. equilibrium;PbSOS C--congruent vaporization;formation. D-D.2 bar O2 , -11 -5 -5 value seems somewhat large, calculations using the resultingo. Zn-O System -13 thermodynamic properties are in excellentThe agreement stable solid with phase is ZnO. Vaporization takes place -1 -7 , -7 Drowart's gas phase equilibria over thepredominantly temperature byrange dissociation of into gaseous Zn and O2 and a 800 1000measurements. 1200 1400 1600 Equilibrium1800 data are availablemuch smaller for PbsOs amount and ofZnO(g). Figures 57-60 show cal- -3 § T (K) -9 -9 Pb60 6 at only one temperature, 1200 culatedK. The entropypartial pressures at 298 for vaporization of ZnO. The K for these two species was estimatedGibbs by extrapolating energy function the of gaseous ZnO was calculated using -5 °2 FIG. 54. PbO congruent vaporization. the estimated internuclear distance of Brewer and Rosenb- -11 -11 values for the monomeric through tetrameric species, and &: the estimated value C;IR = 3.0 was used to calculate val- e -7 -13 -13 ues of the Gibbs energy functions. The gas phase equilibria at t!I 0 -' -9 Pb02 1200 K were then used to derive values of the enthalpies-1 of [ 10-15 BAR O ) PbSOS formation. 2 BOO 1000 1200 1400 1600 1800 -11 -3 T (K) T (1<) Zn "'" o. Zn-O System -5 -5 -13 15 FIG. 53. PbO vaporization in 10-15 bar O2 below 905 K and vaporization of FIG. 56. PbO maximum vaporization rates. A_IO- bar 02; B-Ph-PbOThe stable solid phase is ZnO. Vaporization takes place Ph-PbO mixture above 905 K. equilibrium; C--congruent vaporization;a:: D-D.2 barpredominantly O2 , by dissociation into gaseous Zn anda:: O2, and a e3 -7 e -7 800 1000 1200 1400 1600 1800 much smaller amount ofZnO(g). Figures 57-60 show cal- T (K) culated partial pressures for vaporization of § ZnO. The value seems somewhat large, calculations using the resulting -9 thermodynamic properties are in excellent agreementGibbs energyI with function of gaseous ZnO was calculated using -1 FIG. 54. PbO congruent vaporization. Drowart's gas phase equilibria over the temperaturethe estimated rangeI of internuclear distance of Brewer and-11 Rosenb- measurements. Equilibrium data are available for PbsOsI and -3 Pb 0 at only one temperature, 1200-13 K. The entropyi..-Pb at2 298 -13 6 6 / K for these two species was estimated by extrapolating the -1 -5 °2 [ 10-15 BAR O ) BOO 1000 1200 values for the monomeric through tetrameric1000 1200species, 1400 and1600 1800 2 R.H. Lamoreaux and D.L. Hildenbrand,! T (K) T (1<) &: the estimated value C;IR = 3.0 was used to calculate val- -3 “High-Temperaturee -7 Vaporization Behavior of Oxides II. Oxides of Be, Mg, Ca, Zn "'" ues of the Gibbs energy functions. The gas phase equilibria at 15 Sr,t!I Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg,”! FIG.
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