Cadmium Telluride Thin Films Grown By Atomic Layer Epitaxy

1991 ◽  
Vol 222 ◽  
Author(s):  
Arla Kytökivi ◽  
Yrjö Koskinen ◽  
Aimo Rautiainen ◽  
Jarmo Skarp
Keyword(s):  
Surface Roughness ◽  
Vapor Pressure ◽  
Flow Reactor ◽  
Substrate Surface ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Surface Development ◽  
High Vapor ◽  
Cdte Films ◽  
Cds Film

ABSTRACTPolycrystalline CdTe films up to 2 μm thick were grown by Atomic Layer Epitaxy (ALE) at 350–450°C. The growth was carried out in a lateral flow reactor, using the elements as source materials and 25 cm2 glass/ITO and glass/ITO/SnO2 as substrates. A growth of CdS film by ALE preceded the growth of CdTe.Profilometry, X-ray diffraction analysis and scanning electron microscopy were used to characterize the films.The relatively high vapor pressure of CdTe determined the upper limit of the processing window, while the small vapor pressure of Te2 set a practical lower limit of 390–400°C.The CdTe films were smooth up to 100–500 nm depending on the temperature and the substrate surface. Development of surface roughness was detected as the growth process proceeded. At the same time there was an increase of the effective surface area of the film, observed as a significant increase in the macroscopic growth rate. The greater surface roughness was also evident in the reduced degree of (111) orientation.The CdS/CdTe structure was investigated for its potential in solar cell applications.

OPTICAL PROPERTIES OF CdTe/ZnTe ULTRATHIN QUANTUM WELLS GROWN BY ATOMIC LAYER EPITAXY

2002 ◽  
Vol 09 (05n06) ◽  
pp. 1667-1670 ◽  
Author(s):  
M. GARCÍA-ROCHA ◽  
I. HERNÁNDEZ-CALDERÓN
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Quantum Wells ◽  
Gaas Substrate ◽  
Room Temperature ◽  
Diffusion Length ◽  
Substrate Surface ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Low Temperature Photoluminescence

Ultrathin quantum wells (UTQWs) of CdTe within ZnTe barriers were successfully grown by atomic layer epitaxy (ALE) on GaAs(001) substrates. ALE growth of CdTe was performed by alternate exposure of the substrate surface to individual fluxes of Cd and Te. Two different samples with 2-monolayer (ML) (substrate temperature Ts= 270° C ) and 4 ML (Ts = 290° C ) CdTe QWs were grown. Low temperature photoluminescence (PL) experiments exhibited intense and sharp peaks associated to the 2 ML QWs at 2.26 eV. In the case of the nominally 4-ML-thick QW the PL spectrum presented an intense peak around 2.13 eV and two weak features around 2.04 and 1.91 eV. The first peak is attributed to ~ 3 ML QW and the second one to ~ 4 ML QW. The dominance of the 3 ML peak is mainly attributed to Cd loss in the QW due to its substitution by Zn atoms. Due to a high diffusion length of the photogenerated carriers in the barriers, quite weak signals from the ZnTe barriers were observed in both cases. Room temperature (RT) photoreflectance (PR) spectra showed contributions from the CdTe UTQWs, the ZnTe barriers, and the GaAs substrate.

Low Pressure Diamond Growth Using a Secondary Radical Source

1992 ◽  
Vol 282 ◽  
Author(s):  
Terttu I. Hukka ◽  
Robin E. Rawles ◽  
Mark P. D'Evelyn
Keyword(s):  
Substrate Surface ◽  
Thermal Dissociation ◽  
Chemical Vapor ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Diamond Growth ◽  
Hydrogen Atoms ◽  
Cycle Times ◽  
Novel Method ◽  
Precursor Molecules

ABSTRACTA novel method for chemical vapor deposition and atomic layer epitaxyusing radical precursors under medium vacuum conditions is being developed. Fluorine atoms are generated by thermal dissociation in a hot tube and abstract hydrogen atoms from precursor molecules injected immediately downstream of the source, generating radicals with completechemical specificity. The radical precursors are then transported to the growing substrate surface under nearly collision-free conditions. To date we have grown diamond films from CCl3 or CH3 radicals together with atomic hydrogen, generated by injecting CHCI3 or CH4 and H2 into the F atom stream at reactor pressures between 10−4 and 10−2 Torn This approach should be ideal for low-temperature growth and atomic layer epitaxy: growth rates remain relatively high because activation energies for radical reactions are typically small and because the cycle times for atomic layer epitaxy can be reduced to die msec range by fast gas-stream switching, and contamination and segregation are minimized by keeping the surface “capped” by chemisorbed intermediates.

Novel Zirconium Formamidinate Precursor for the ALD of ZrO2

2009 ◽  
Vol 1194 ◽  
Author(s):  
Huazhi Li ◽  
Deo V Shenai ◽  
Jean-Sebastien Lehn
Keyword(s):  
Thin Films ◽  
Thermal Stability ◽  
Atomic Layer Deposition ◽  
Vapor Pressure ◽  
Zirconium Oxide ◽  
Atomic Layer ◽  
High Thermal Stability ◽  
High Vapor Pressure ◽  
Layer Deposition ◽  
High Vapor

AbstractZirconium tetrakis(N,N’-dimethylformamidinate), Zr-FAMD, was synthesized and evaluated as a precursor for the deposition of zirconium oxide (zirconia) thin films via Atomic Layer Deposition (ALD) technique. Zr-FAMD has a high vapor pressure and displays an exceptionally high thermal stability; it is thus well-suited to be used as a precursor for the deposition of zirconia thin films. Zr-FAMD is a more ideally-suited precursor than tetrakisethylmethylaminozirconium or TEMAZr, which has an equivalent vapor pressure, but is plagued with a rather low thermal stability, limiting its usefulness at high deposition temperatures. Zr-FAMD can be used to deposit zirconia thin films at temperatures as high as 375 °C without evidence of decomposition.

Atomic layer epitaxy and characterization of CdTe films grown on CdTe (110) substrates

1983 ◽  
Vol 54 (10) ◽  
pp. 6047-6050 ◽  
Author(s):  
M. Pessa ◽  
P. Huttunen ◽  
M. A. Herman
Keyword(s):  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Cdte Films

Beam Assisted Atomic Layer Controlled Epitaxy and Etching of GaAs

1991 ◽  
Vol 222 ◽  
Author(s):  
T. Meguro ◽  
Y. Aoyagi
Keyword(s):  
Laser Irradiation ◽  
Etch Rate ◽  
Substrate Surface ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Optical Absorption Band ◽  
Photon Irradiation ◽  
Visible Wavelength ◽  
Site Selectivity ◽  
Surface Decomposition

ABSTRACTAtomic layer epitaxy (ALE) using laser irradiation and digital etching of GaAs are described herein.Epitaxy: We have succeeded in the laser-assisted ALE (laser-ALE) of GaAs using visible wavelength Art laser irradiation and an alkylgallium source. Visible wavelength photon irradiation induces surface decomposition but not volume decomposition of alkylmetal molecule source gases. ALE is realized by the enhancement of decomposition of alkylgallium molecules only on the As-terminated surface but not on the Ga-terminated surface. This site-selectivity of alkylgallium decomposition is induced by the optical absorption band broadening, which is due to the chemisorption of alkylgallium at the As-terminated surface.Etching: In ditigal etching, etchant gas pulses and an energetic beam sequentially impinge onto the substrate surface. In the Ar+/Cl2 system, the etch rate is found to be independent of both Cl2flux and Ar+ beam density, and the etch rate saturates at a level below one monolayer per cycle. By using Cl radicals as etchants instead of Cl2, the self-limited etching characteristics of digital etching are obtained within both the Ar+ incidence time and Cl feed time of the etching cycle.

Surface roughness reduction in atomic layer epitaxy growth of titanium dioxide thin films

1994 ◽  
Vol 249 (2) ◽  
pp. 155-162 ◽  
Author(s):  
M Ritala ◽  
M Leskelä ◽  
L Niinistö ◽  
T Prohaska ◽  
G Friedbacher ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Titanium Dioxide ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Titanium Dioxide Thin Films

Cadmium Sulphide Thin Films Grown By Atomic Layer Epitaxy

1991 ◽  
Vol 222 ◽  
Author(s):  
Aimo Rautiainen ◽  
Yrjö Koskinen ◽  
Jarmo Skarp ◽  
Sven Lindfors
Keyword(s):  
Thin Films ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Inorganic Compounds ◽  
Substrate Surface ◽  
Cadmium Sulphide ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Elemental Reactants ◽  
Cds Films

ABSTRACTPolycrystalline cadmium sulphide (CdS) thin films were grown by Atomic Layer Epitaxy (ALE) using indium tin oxide and tin oxide coated glass substrates. Some of the experiments were made using elemental reactants, and others with inorganic compounds as reactants. Films were characterized using various techniques such as XRD, SEM and optical transmission spectroscopy. Growth rate of CdS films was observed to be 1/4 - 1/3 monolayer per cycle with elemental reactants. A full monolayer/cycle coverage was obtained when using CdCl2 and H2S as reactants. The crystalline structure of the CdS films wis β-cubic (111) when using elemental reactants. The mixed structure was observed when inorganic compounds were used as reactants. Only the hexagonal phase was observed, when substrate surface was pretreated before CdS deposition.

Zur Bildung von Mg2Si- und CaSi2-Schichten auf einkristallinen Siliciumsubstraten

1980 ◽  
Vol 35 (11) ◽  
pp. 1268-1270 ◽  
Author(s):  
R. Braungart ◽  
H. Sigmund
Keyword(s):  
Surface Roughness ◽  
Vapor Pressure ◽  
Layer Thickness ◽  
Silicon Surface ◽  
Metal Vapor ◽  
Thin Layers ◽  
Silicon Substrates ◽  
Oriented Growth ◽  
High Vapor Pressure ◽  
High Vapor

Abstract Thin layers of Mg2Si or CaSi2 (10-20 μm) on silicon substrates can be prepared by the reaction of the corresponding metal vapor with silicon wafers. The resulting poly crystal line silicides have a purity of more than 99.95%; their surface roughness is about 2 μm. The layer thickness and the dimensions of the crystallites may be controlled by the conditions of the preparation. An oriented growth on the <111>-silicon surface is observed in the case of CaSi2- The method described seems generally well suited for growing silicide layers of metals with high vapor pressure. The Mg2Si- and the CaSi2-layers were used as starting material in a special "sandwich"-epitaxy in order to prepare Mg- and Ca-doped Si-layers.

Atomic Layer Epitaxy: modeling Of Growth Parameters for Device Quality GaAs.

1989 ◽  
Vol 145 ◽  
Author(s):  
E. Colas ◽  
R. Bhat ◽  
G. C. Nihous
Keyword(s):  
Initial Conditions ◽  
Growth Parameters ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Impurity Incorporation ◽  
Gas Concentration ◽  
Group Iii ◽  
Sequential Group

AbstractDevice quality GaAs was grown in a conventional Organometallic Chemical Vapor Deposition (OMCVD) reactor, using sequential group III and V reactant gas exposures typical of Atomic Layer Epitaxy (ALE). The importance of gas phase concentration transients during the ALE cycles was revealed by systematic investigations of the effect of the sequences used, for the cycles, on impurity incorporation as well as on the growth rates. In this study, we attempt to quantify the effects of such transients by solving the diffusion equation for the reactant gases, with initial conditions specific to ALE. We used this model to calculate the time dependence of the reactant gas concentration at the growing surface. This quantitative study gives us new insights into the ALE technique and confirms that the V/II ratio at the substrate surface can be controlled by the choice of the gas sequence.

Sign in / Sign up

Export Citation Format

Share Document