Low Pressure Mocvd of Copper Based Compounds for Photovoltaic Applications

Abstract

In recent years copper based compounds such as copper indium diselenide (CuInSe,, CIS) have emerged as the most promising candidates for high efficiency stable solar cells. To date research has been centred around the standard thin film deposition techniques i.e. evaporation, sputtering and electroplating. While these techniques give good films it has proved difficult to gain reproducible results. The production of devices based on CIS thin films has now progressed to a point where, to achieve further advances in device efficiency, more research into alternative deposition techniques and the basic deposition parameters is required. The major problems encountered with the standard technique are poor step coverage and lack of control over the stoichiometry. A low pressure MOCVD reactor has been constructed to investigate the growth of thin film CIS and the factors affecting deposition. The considerations involved in the design of such a system are discussed. A detailed study of reactor parameters affecting low pressure MOCVD of copper, copper indiurn and copper indium diselenide is being carried out. Mass spectrometric analysis of the decomposition products has been undertaken and the growth mechanisms and kinetics involved in these deposition processes are being investigated.

Alcohol-Assisted Deposition of Copper Films from Supercritical Carbon Dioxide

“…The high solubility of Cu(II)(β-diketonate) 2 in alcohols has been used in CVD to develop a simple liquid delivery system which provides highly accurate, reproducible, and controllable flow. [33][34][35][36] Furthermore, many Cu(II)(β-diketonate) 2 species such as Cu(hfac) 2 coordinate reversibly to alcohols and form adducts. 37,38 Some of these adducts have higher vapor pressures and lower melting points than the corresponding Cu(II)(β-diketonate) 2 , 39,40 rendering them better precursors for CVD.…”

“…This enhancement is partly due to improved delivery. The high solubility of Cu(II)(β-diketonate) 2 in alcohols has been used in CVD to develop a simple liquid delivery system which provides highly accurate, reproducible, and controllable flow. − Furthermore, many Cu(II)(β-diketonate) 2 species such as Cu(hfac) 2 coordinate reversibly to alcohols and form adducts. , Some of these adducts have higher vapor pressures and lower melting points than the corresponding Cu(II)(β-diketonate) 2 , , rendering them better precursors for CVD. Apart from the improved transport, alcohols, introduced in the system as solvents or additives, or coordinated to the precursor in an adduct, can act as reducing agents.…”

Syntheses, Structures, and Thermal Behavior of Cu(hfacac) Complexes Derived from Ethanolamines

“…In our previous studies we found that H 2 O facilitates the release of the hfacac ligand from the Cu(hfacac) 2 (H 2 O), 2 , precursor by a proton transfer . Other workers found an addition of alcohols such as ethanol and 2-propanol into the CVD system to be beneficial for the reduction of the precursor to copper metal. − Unfortunately, both water and alcohols form adducts with Cu(hfacac) 2 that are unstable at a reduced pressure in the gas phase. Therefore, an excess of these coreactants has to be added for the reaction to take place.…”

Solution Delivery of Cu ( hfac ) 2 for Alcohol‐Assisted Chemical Vapor Deposition of Copper

“…The disproportionation of various Cu(I) mono-␤-diketonates generally gives the highest deposition rates and has received the greatest attention for potential commercialization 4 2Cu (I) (hfac)(VTMS) c r Cu (0) ϩ Cu (II) (hfac) 2 ϩ 2VTMS [1] The reduction of Cu(II) di-␤-diketonates gives slower rates, but the precursors are more stable and somewhat easier to handle 5 Cu (II) (hfac) 2 ϩ H 2 r Cu (0) ϩ 2H(hfac) [2] There have been several reports that the growth rates for Cu(hfac) 2 reduction can be improved using H 2 O or alcohols as coreactants. [6][7][8] For example, we were able to obtain growth rates of 3 mg cm Ϫ2 h Ϫ1 when 5 Torr of isopropanol vapor (i-PrOH) was added to the H 2 carrier gas as a coreactant. 9 In comparison, we have reported that the direct reduction of Cu(hfac) 2 using pure H 2 as the carrier gas gives a maximum growth rate of 0.5 mg cm Ϫ2 h Ϫ1 at the same operating conditions (i.e., 300ЊC and 40 Torr H 2 pressure).…”