|Highligth 1 |
Atomic layer deposition (ALD) is a chemical vapor-based thin film deposition technique which relies on the sequential and self-terminating gas–surface reactions of two gaseous reactants. It enables atomic level thickness control, tunable film composition and an unmatched ability to produce conformal films on complex 3D-shaped surfaces. Indeed, ALD has emerged as a mainstream deposition tool for many industrial and research applications in the fields of micro-electronics and energy.
To improve control over the ALD process, and ultimately the ability to tailor the properties of nanostructured materials atomically, we use a custom built reactor that we move to Synchrotron Radiation facilities (SOLEIL, ESRF)
A complementary suite of in situ synchrotron X-ray techniques (fluorescence, reflectivity, grazing-incidence diffraction, absorption) has been used to investigate both structural and chemical evolution during ZnO ALD on a-SiO2 (amorphous), c- Al2O3 (cristalline) and In0.47Ga0.53As substrates [1, 2, 3], enable us to gain a deep understanding of growth behavior and elucidate the atomistic processes taking place during the initial stages of growth.
| Evolution of Crystal Structure During the Initial Stages of ZnO Atomic Layer Deposition. R. Boichot et al., J. Chem. Mater. (2016) 28, 592 |
 An Atomistic View of the Incipient Growth of Zinc Oxide Nanolayers. M. H. Chu et al., Cryst. Growth Des. (2016) 16, 5399
 SIRIUS: A new beamline for in situ X-ray diffraction and spectroscopy studies of advanced materials and nanostructures at the SOLEIL Synchrotron G. Ciatto et al., Thin Solid Films (2016) 617, 48
|Highligth 2 |
The Initial Stages of ZnO Atomic Layer Deposition on Atomically Flat In0.53Ga0.47As Substrates
ZnO has been identified a good candidate material to be inserted as a tunneling insulator layer at the metal- In0.53Ga0.47As junction. A key consideration in many modern devices is the atomic structure of the hetero-interface, which often ultimately governs the electronic or chemical process of interest. A complementary suite of in situ synchrotron X-ray techniques (ﬂuorescence, reﬂectivity and absorption) as well as modeling was used to investigate both structural and chemical evolution during the initial growth of ZnO by atomic layer deposition (ALD) on In0.53Ga0.47As substrates . Prior to steady-state growth behavior, we discover a transient regime characterized by two stages. First, substrate-inhibited ZnO growth takes place on InGaAs terraces. This leads eventually to the formation of a 1-nm-thick, two-dimensional (2D) amorphous layer. Second, the growth behavior and its modeling suggest the occurrence of dense island formation, with an aspect ratio and surface roughness that depends sensitively on the growth condition. Finally, ZnO ALD on In0.53Ga0.47As is characterized by 2D steady-state growth with a linear growth rate of 0.21 nm.cy−1, as expected for layer-by-layer ZnO ALD.
 The Initial Stages of ZnO Atomic Layer Deposition on Atomically Flat In0.53Ga0.47As Substrates E. Skopin et al., Nanoscale (2018)
|Ensemble averaged nanowire polarity determined by X-ray anomalous diffraction (X-ray resonant scattering). |
Polarity is an intrinsic property of non-centrosymmetric crystalline structures such as GaN or ZnO wurtzite which is determined at the early stage of growth. Therefore, the knowledge of the NWs polarity for different growth parameters, substrate and surface preparations gives, in turn, much information on the NWs growth mechanism. Besides, the nanowire polarity affects surface configuration so the reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device. Anomalous Diffraction (or resonant X-ray scattering) was used to study GaN NWs grown by PAMBE directly on Si substrate . Experimental data clearly shows that as grown-NWs are N-polar (the up ended - NWs are Ga-polar). A similar study was performed to demonstrate the polarity transfert from ZnO seed layer grown by Chemical Bath Deposition on Si substrate to CBD ZnO nanowires .
| Other relevant papers |
 Polarity of GaN Nanowires Grown by Plasma-Assisted Molecular Beam Epitaxy on Si(111). K. Hestroffer, C. Leclere, C. Bougerol, H. Renevier, Bruno Daudin. Phys. Rev. B 84, (2011), 245302.
 XAFS atomistic insight of the oxygen gettering in Ti/HfO2 based OxRRAM. R. Viennet, H. Roussel, L. Rapenne, J. L. Deschanvres, V. Jousseaume, E. Jalaguier, M.G. Proeitti, H. Renevier. Phys. Rev. Mater. 2, (2018), 055002.
 Diffraction Anomalous Fine Structure : basic formalism. H. Renevier, M.G. Proietti. International Tables for Crystallography I. Accepted.
 Diffraction Anomalous Fine Structure : experiment and data analysis. H. Renevier, M.G. Proietti. International Tables for Crystallography I. Accepted.
Written by Maria Carmen Jimenez Arevalo
Date of update June 6, 2018