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CHARACTERIZATION OF AMORPHOUS SILICON ALLOYS THROUGH TEHERMAL HYDROGEN EFFUSION

Objective



THE PRESENT RESEARCH PROGRAM DEALS WITH THE H CHARACTERIZATION OF THIN FILMS OF A-SI:H, INTRINSIC, DOPED AND ALLOYED. THE METHOD USED STANDS IN THE PROGRESSIVE THERMAL DEGRADATION, WHICH APPLIES TO ANY TYPE OF HYDROGENATED THIN FILMS AND CONSTITUTES A VERY USEFULL APPROACH FOR THE STUDY OF THEIR RELIABILITY THROUGH THEIR H STABILITY. IT ALSO PROVIDES THE H CONTENT AND ALLOWS TO DETECT H SITES OF DIFFERENT STABILITIES. MOREOVER IT INFORMS ABOUT THE FILMS MICROSTRUCTURE, EVIDENCING THE EVENTUAL PRESENCE OF TWO PHASES, A POROUS - LOW DENSITY- ONE WITH INTERCONNECTED MICROVOIDS AND RICH IN WEAK H SITES (WHS) AND ANOTHER ONE OF HIGHER DENSITY. THESE INFORMATIONS ARE OF PRIME IMPORTANCE IN ORDER TO OPTIMIZE THE TECHNOLOGICAL PARAMETERS FOR A STILL NECESSARY IMPROVEMENT OF THE FILMS PERFORMANCES. IT IS WELL KNOWN THAT THE H PLAYS AN INDISPENSABLE ROLE BY REDUCING THE DENSITY OF ELECTRONIC DEFECTS. IT IS THUS CRUCIAL TO STUDY ITS STABILITY TO IMPROVE THE DEVICES ENDURANCE, IN PARTICULAR AGAINST SUN DAMAGE IN SOLAR CELLS.

THE STUDIES UNDERTAKEN HAVE EVIDENCED DIVERSE CORRELATIONS BETWEEN THE FILMS H CHARACTERISTICS AND THE TECHNOLOGICAL PARAMETERS, THEREFORE ALLOWING TO SELECT THEM IN WAY TO MINIMIZE THE PROPORTION OF WHS, THUS IMPROVING THE FILMS STABILITY. BESIDES, THE RESULTS OBTAINED ALONG THIS THREE YEARS RESEARCH PROGRAM HAVE ALLOWED US TO DEVELOP A MODEL FOR THE ANTURE AND THE DEGRADATION MECHNAISM OF THE WHS. IT IS PROPOSED THAT THE WHS OF THE LIGHT-INDUCED DEGRADATION IS THE SAME AS THE ONE FO THE THERMAL DEGRADATION, A WHS BEING FROMED EACH TIME TWO SI-H BONDS ARE IN CLOSED CONTACT, WHICH ALLOWS THEM TO REACT WHEN ACTIVATED. WHS ARE THUS CONSTITUED BY PAIRS OF NEIGHBORING H BONDS, MOJORITALY LOCATED ON THE MICROVOIDS WALL. CONSEQUENTLY THE REDUCTION OF THESE WHS IMPLIES THE REDUCTION OF THE MICROVOIDS POPULATION, WHICH IN TURN REQUIRES THE CONTROL OF THE MICROSTRUCTURE DURING FILMS GROWTH, AN ESSENTIAL PRECURSOR TO THE MASTERING OF THE IMPROVEMENT OF THE FILMS PERFORMANCES AND THEIR STABILITY.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSITAT DE BARCELONA
Address
Gran Via De Les Corts Catalanes 585
Barcelona
Spain