Growth of zinc blende MgS/ZnSe single quantum wells by molecular-beam epitaxy using ZnS as a sulphur source

Bradford, C.; O'Donnell, C B; Urbaszek, B.; Balocchi, Andréa; Morhain, C.; Prior, K. A.; Cavenett, B.C.

doi:10.1063/1.126824

Cited by 56 publications

(55 citation statements)

References 10 publications

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“…Trends in the series BeO through BaO [10] and BeS through BeTe [15,19,23] were described. BeS [6,9,12,17] and MgS [25,33,40] represent materials worth mentioning. Not only closed-shell parent systems, but also radical-ions [13,14,27a,29,35,36] derived from them were subjects of studies, sometimes by means of photoelectron spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Small Group IIa–VIa Clusters and Related Systems: A Theoretical Study of Physical Properties, Reactivity, and Electronic Spectra

Srnec

Zahradník

2007

Eur J Inorg Chem

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In the monomeric form, the title systems assume unexpected optical properties, and as oligomers they can serve as candidates for molecular devices. In bulk they are attractive in the area of material science. A broad set of quantum chemical methods ranging from density functional theory by the Hartree-Fock method and the Møller-Plesset perturbation theory to the coupled-cluster method, in connection with nonrelativistic Dunning's basis sets as well as with relativistic SDD basis sets were used. Electronic spectra were analyzed by means of time-dependent DFT, with the symmetryadapted cluster configuration interaction and with the internally contracted multireference configuration interaction. The Douglas-Kroll-Hess quasirelativistic Hamiltonian served as a basis for the estimation of the role of relativistic effects. All the diatomics representing 25 elements of a matrix formed by the combination of group IIa (Be, ..., Ba) with group VIa (O, ..., Po) atoms were characterized by calculated bond length, valence vibration, dipole moment, and the HartreeFock frontier orbital energies. Calculated characteristics were confronted with experimental data. The geometry of the oligomers (from dimers through hexamers) was investigated systematically, and the nature of the located stationary

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Section: Introductionmentioning

confidence: 99%

Small Group IIa–VIa Clusters and Related Systems: A Theoretical Study of Physical Properties, Reactivity, and Electronic Spectra

Srnec

Zahradník

2007

Eur J Inorg Chem

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“…Recently, our group has demonstrated that a simple modification to the MBE growth process can be used to grow much thicker layers of both MgS [12,13] and MnS [14] in the ZB structure. In this paper, we review the growth process and subsequently describe some results obtained from structures containing both MgS and MnS.…”

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confidence: 99%

Growth by MBE and characterization of metastable group II sulphides

Prior

Bradford

David

et al. 2004

Physica Status Solidi (b)

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Many group II sulphides semiconductors have the rocksalt structure as their stable crystal structure. In the case of MgS and MnS it has been demonstrated that these compounds can be grown in the metastable zinc blende structure. Recently, at Heriot-Watt we have shown that a simple MBE growth procedure can be used to increase the thickness of these metastable layers to over 130 nm. In this paper, we summarise some of the results we have obtained and describe some of the structures which we have grown using these materials. The aim is to demonstrate that the growth method is simple, and that MgS in particular is a material with useful properties that can be incorporated into a variety of structures. Finally, we describe some potential uses of these compounds which we have not yet explored, and suggest other compounds which may be successfully grown with this method.1 Introduction It is possible, using a variety of methods, to produce compounds in crystal states which are not their lowest energy configurations. Perhaps the best-known example of this is carbon, where the well-known diamond structure is metastable with respect to the graphite structure. In the case of II-VI compounds, using thin film growth techniques such as MBE and MOCVD it is possible to grow compounds and alloys in the zinc blende (ZB) phase when this is not the lowest energy state. Examples are the growth of CdSe [1] and CdS [2] on (100) oriented substrates where the fourfold periodicity of the underlying layer causes adoption of the ZB phase rather than the lower energy wurtzite phase. II-VI compounds are different to III-Vs in the variety of crystal structures that they can adopt. In addition to ZB and wurtzite, the NaCl (rocksalt) structure is found. The lowest energy crystal structure which is adopted can be related to the ionicity f i of the compound and for f i < 0.625 II-VI compounds adopt the ZB structure [3]. Above this value the wurtzite structure occurs, with a transition to the rocksalt structure when f i < 0.78 [4].Unlike the compounds which have wurtzite as their stable phase that can be made to adopt the ZB structure on (001) surfaces, there is no symmetry requirement which can force the adoption of ZB instead of rocksalt. In this case both structures are cubic, and the differences are that atoms incorporated into a ZB layer have 4 nearest neighbours instead of 6 as is found in the rocksalt structure.In recent years, effort has gone in to exploring the growth of metastable ZB compounds, particularly MgS and MnS, which have similar lattice constants to GaAs. MgS is of particular interest as its Philips' ionicity is 0.786, placing it close to the rocksalt stability boundary [5]. Initial attempts to grow MgS by MBE produced ZB layers only 0.96 nm thick before changes in the RHEED pattern were observed which were believed to correspond to a change in the crystal structure to rocksalt [6]. Subsequent MOCVD growth obtained layers up to 10 nm thick in the ZB crystal structure [7] which were of high quality and could be incorporated in MgS...

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“…• C allows one to grow MgS layers of necessary thickness without transformation to a rock-salt phase [6].…”

Section: Methodsmentioning

confidence: 99%

“…The middle of the stop-band was chosen to correspond to a standard ZnCdSe QW wavelength, which is ≈ 520 nm. It has been pointed out by Bradford et al [6] that pseudomorphic growth of zinc-blende MgS on GaAs is only possible under low temperatures and is limited by a certain critical thickness depending on the temperature. These constraints do not allow growing of a pure MgS/ZnSe DBR with λ/4-thick layers.…”

Section: Bragg Mirror Designmentioning

confidence: 99%

“…For example, Suemune et al have grown a 5-period ZnSe/(ZnSe/MgS) distributed Bragg reflector (DBR) with a 92% reflectivity by metal-organic vapor phase epitaxy [4]. Kruse et al have demonstrated 17-period DBR of the same type with 99% reflectivity, grown by molecular beam epitaxy (MBE) using a valved cracker cell as a sulphur source [5].Earlier Bradford et al have suggested to employ ZnS as a sulphur source to grow MgS/ZnSe quantum wells (QWs), using the efficient Mg-Zn exchange interaction which is due to the much stronger Mg-S binding energy as compared to the Zn-S one, although they have not applied this technique to DBRs [6]. This paper reports on the studies of novel design (ZnSe/MgS)/ZnCdSe DBRs grown by MBE using ZnS as a sulphur source.…”

Section: Introductionmentioning

confidence: 99%

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