Data structure
Structure of the base is presented in the appendix. Only the most important tables are shown together with relations between them.
From a user’s point of view the data structure is as follows:
• material description and data,
• sample description and data,
• measurement parameters and file name,
• computed results and file name.
The
diagram shows a tree structure of the information stored in a database according
to the above scheme.
Material is specified throughout the database by its unique identifier. It is a text consisting of up to 18 characters. This identifier is also stored in measurement data files. Other information describing the material is stored in the base only. It consists of a material description (text up to 255 characters), defect description (text up to 255 characters), dielectric constant, Richardson constant, effective mass for electrons and holes.
Sample is specified throughout the database by its identifier, unique in given material context (i.e. sample name together with the material name identifies the sample in unique way). It is a text consisting of up to 16 characters. This identifier is also stored in the measurement data files. Other information describing the sample is stored in the base only. It consists of the sample description (text up to 255 characters), its area and capacitance with zero bias voltage applied.
Measurement is specified throughout the database by its unique identifier. It is an internally assigned number and is not intended to be used directly by a system user, although it is displayed on a presentation screens. Each measurement entry contains a reference to the sample description, measurement type identifier, date of measurement and a set of measurement parameters (such as temperature of the sample, its illumination, magnetic field applied) which can be specific for different types of measurements. It may consists of up to 24 double numbers, up to 10 integers, two Boolean parameters, two strings of up to 255 characters each, date parameter and a text field of virtually unlimited length (~65000 characters). However, the most important item stored is the name and position (full path) of a measurement data file. Parameter sets for different measurement types are user-definable through a specially designed interface form.
Result is specified throughout the database by its unique identifier. It is an internally assigned number and is not intended to be used directly by a system user, although it is displayed on appropriate presentation screens. Each result entry contains a reference to the measurement description, the computing method used to obtain the data and the name and position (full path) of the result data file.