A modern courtyard will likely be quite minimal in design, which can create a feeling of openness, space and light which is very relaxing for sitting in. At the same time a great minimal design will also be easier to clean as their will be fewer items to get behind and to clean underneath. This means that you can maintain it easily and keep it looking as fresh and slick as it did when you got it installed.
For the ground you will likely choose some kind of tiles which can be a range of materials from marble to concrete. Either way, you should try to use a light colour so that you again create more feeling of space and cleanliness in your space and whites, light greys and beige are always good options as darker or brighter colours can end up feeling more oppressive. You might also want to get your concrete or tiles printed or stained in order to add another element to them, this way you can create marble like patterns which will not only hide dirt and dust, but also make space more attractive and more expensive looking. Shapes stamped onto the tiles, or the use of different shades can be what helps to create interest in your modern courtyard design ideas and this is something you should talk through with a designer.
To maintain this modern looking design you should also be sure to get maintenance for your tiles and this will prevent things like pot holes etc from forming which will make your tiles look untidy and dirty. You can also get underfloor heating for your tiles however to prevent this and this is an aspect of modern courtyard design that is quite practical.
You will also want some form of seating in your courtyard, and you should have somewhere nice to sit while you read your book outside as well as somewhere social for people to gather when you have guests (courtyards are perfect for parties). Try and choose a seat that continues the modern minimalist look but that also offers comfort while being suited to an outdoors location.
Modern courtyard designs also need some kind of feature and there are a range of features you can use here - from a pond to a fountain to a statue or plants and trees. This will make your courtyard more than just an open space and will give something to look at. With a fountain or pond you also get the sense of purity that comes with water as well as the trickling noise and the constant movement which can add a lot to a courtyard. The correct mood lighting, in conjunction with this water, can cast patterns around the whole area. Have sliding glass doors leading onto your courtyard to ensure that you can appreciate it while indoors too.